He hath compassed the waters with bounds - The word rendered "compassed" (חוּג chûg), means to describe a circle - to mark out with a compass; and the reference is to the form of the horizon, which appears as a circle, and which seems to be marked out with a compass. A similar idea Milton has beautifully expressed in his account of the creation:
"Then staid the fervid wheels, and in his hand
He took the golden compasses, prepared
In God's eternal store, to circumscribe
This universe, and all created things:
One foot he centered, and the other turned
Round through the vast profundity obscure;
And said, 'Thus far extend thy bounds,
This be thy just cirrumference, O world! '"
Paradise Lost, B. vii.
In the passage before us, we have a statement of the ancient views of geography, and of the outer limits of the world. The earth was regarded as a circular plane, surrounded by waters, and those waters encompassed with perpetual night. This region of night - this outer limit of the world, was regarded as at the outer verge of the celestial hemisphere, and on this the concave of heaven seemed to rest. See Virgil, Geor. i. 247.
Illie, ut perhibent, aut intempesta silet nox
Semper, et obtenta densantur, nocte tenebrae;
Aut redit a nobis Aurora, diemque redicited
No maps are preserved constructed at so early an age as the time of Job; but maps have been constructed from the descriptions in Strabo, Herodotus, and others, which furnish illustrations of the prevailing views on the subject of geography in their times. The oldest geographical writer among the Romans is Mela, who lived in the reign of Claudius, and who died 54 a.d. In his work, De Situ Orbis, he gives a description of the world according to the prevailing views, and probably embodied the results of former investigations and discoveries. "We find him adopting, in its fullest extent, the belief of a circumambient ocean; and when he speaks of the high earth in this middle part of it, and describes the sea as going under and washing round it, we are led to believe, that he viewed the earth as a sort of cone, or as a high mountain raised by its elevation above the abyss of waters. Having made a vague division of the world into East, West, and North, he distributed it into five zones, two temperate, one torrid, and two frigid. Only the first two were habitable; and that on the South was inacessible to man, on account of the torrid regions intervening. According to this system, however, there was on that side another earth, inhabited by people whom he calls Antichthones, from their opposite position with respect to that part which we inhabit.
The form and boundaries of the known and habitable earth are thus delineated: The Mediterranean, with its branches of the Straits, the Euxine, and the Palus Moeotis; its great tributaries, the Nile and the Tanais - these combine, in his conception, to form the grand line by which the universe is divided. The Mediterranean itself separates Europe from Africa; and these continents are bounded on the East, the former by the Tanais, the latter by the Nile; all beyond or to the East of these limits was Asia." The following cut is probably a correct representation of his system, and gives the view of the world which prevailed in his time.
The ancient Arabs supposed the earth to be encompassed with an ocean. This ocean was called the "sea of darkness;" and the Northern sea was regarded as particularly pitchy and gloomy, and was called "the sea of pitchy darkness." Edrisi, a distinguished Arabic geographer of the middle ages, supposed that the land floated on the sea, only a part of it appearing above the water, like an egg, floating in the water.
A map of the world, constructed during the Crusades, and embodying the views of the world prevailing then, exhibits the world, also, as surrounded by a dark ocean on every side - mare tenebrosum - and may be introduced as an illustration of this passage in Job. It is the map of Sanudo, annexed to Bongar's "Gesta Dei per Francos." In this map, Jerusalem, according to the prevailing views, "is placed in the center of the world, as the point to which every other object is to be referred; the earth is made a circle, surrounded by the ocean, the shores of which are represented as every where nearly equidistant from that spiritual capital, the site of which is, indeed, remarkable for its relation to the three continents, Asia, Europe, and Africa. Persia stands in its proper place; but India, under the modifications of Greater and Lesser, is confusedly repeated at different points, while the river Indus is mentioned in the text as the Eastern boundary of Asia. To the North, the castle of Gog and Magog, an Arabian feature, crowns a vast range of mountains, within which, it is said, that the Tartars had been imprisoned by Alexander the Great. The Caspian appears, with the bordering countries of Georgia, Hyrcania, and Albania; but these features stand nearly at the Northern boundary of the habitable earth. Africa has a sea to the South, stated, however, to be inaccessible, on account of the intensity of the heat. The European countries stand in their due place, not even excepting Russia and Scandinavia, though some oversights are observable in the manner in which the two are connected together."
A similar view prevails among the modern Egyptians. "Of geography, the Egyptians, in general, and with very few exceptions, the best instructed among them, have scarcely any knowledge. Some few of the learned venture to assert that the earth is a globe, but they are opposed by a great majority of the 'Ooláma. The common opinion of all the Moos'lims is, that the earth is an almost plane expanse, surrounded by the ocean, which they say is encompassed by a chain of mountains called Cka'f." Lane's Modern Egyptians, vol. i. p. 281. A similar view of the world prevails, also, now among the Independent Nestortans, which may be regarded as the ancient prevailing opinion in Persia, handed down by tradition. "According to their views of geography," says Dr. Grant, "the earth is a vast plain, surrounded by the ocean, in which a leviathan plays around, to keep the water in motion, and prevent its becoming stagnant and putrid; and this leviathan is of such enormous length, that his head follows his tail in the circuit round the earth! That I had crossed the ocean, where I must have encountered the monster, was a thing almost incredible."
The Nestortans, p. 100. In ancient times, it was regarded as impossible to penetrate far into the sea surrounding the earth, on account of the thick darkness, and it was believed that after sailing for any considerable distance on that sea, the light would wholly fail. In the ninth century, the Arabic historians tell us, that the brothers Almagrurim sailed from Lisbon due west, designing, if possible, to discover the countries beyond the "sea of darkness." For ten or eleven days, they steered westward; but, seeing a storm approaching, the light faint, and the sea tempestuous, they feared that they had come to the dark boundaries of the earth. They turned, therefore, south, sailed twelve days in that direction, and came to an island which they called Ganam, or the island of birds, but the flesh of these birds was too bitter to be eaten. They sailed on twelve days further, and came to another island, the king of which assured them that their pursuit was vain; that his father had sent an expedition for the same purpose; but that, after a month's sail, the light had wholly failed, and they had been obliged to return. A great amount of interesting and valuable information, on the ancient views of the geography of the world, may be seen in the Encyclopedia of Geography, vol. i. pp. 9-68. It is not easy to ascertain what were the exact views in the time of Job, but it is quite probable, from the passage before us, that the earth was supposed to be surrounded by an ocean, and that the outer limits were encompassed with deep and impenetrable darkness.
Until the day and night come to an end - Margin, "end of light with darkness." The true meaning is, to the confines of light and darkness. To the end, or extremity תכלית taklı̂yth - perfection, completions) of the light with the darkness; that is, where the light terminates in the darkness. Where that limit was, or how the sun was supposed to pass around it, or could pass over it, without illuminating it, it is now impossible to ascertain. The prevailing views on geography and astronomy must have been very obscure, and there must have been many things which they could not pretend to comprehend or explain.

He hath compassed the waters with bounds - Perhaps this refers merely to the circle of the horizon, the line that terminates light and commences darkness, called here עד תכלית אור עם חשך ad tachlith or im chosech, "until the completion of light with darkness." Or, if we take תכלית tachlith here to be the same with תכלת techeleth, Exodus 25:4, and elsewhere, which we translate blue, it may mean that sombre sky-blue appearance of the horizon at the time of twilight, i.e., between light and darkness; the line where the one is terminating and the other commencing. Or, He so circumscribes the waters, retaining them in their own place, that they shall not be able to overflow the earth until day and night, that is, time itself, come to an end.

He hath (h) compassed the waters with bounds, until the (i) day and night come to an end.
(h) That is, he hid the heavens which are called his throne.
(i) So long as this world endures.

He hath compassed the waters with bounds,.... Not the waters above the firmament, compassed by that, as if Job was contemplating on and discoursing about what is done in the heavens above; though the Targum seems to incline to this sense, paraphrasing the words,
"he hath decreed that the firmament should be placed upon the face of the waters unto the end of light, with darkness;''
but the waters of the sea, Job descending now to consider the waters of the great deep, and the wonderful restraint that is laid upon them; which is as astonishing as the binding up of the waters in the clouds without being rent by them; for this vast and unwieldy body of waters in the ocean Jehovah manages with as much ease as a mother or nurse does a newborn infant, makes the cloud its garment, and thick darkness a swaddling band for it, Job 38:8; he has as it were with a compass drawn a line upon the face of it; he has broke up for it its decreed place, and set bars, and doors, and bounds to its waves, that they, nay come no further than is his pleasure, as is observed in the same place; the bounds he hath compassed it with are the shores, rocks, and cliffs, so that the waters cannot return and cover earth, as they once did; yea, which is very surprising, he has placed the sand, as weak and fluid as it is, the bound of the sea by a perpetual decree; so that though its waves toss and roar, they cannot prevail, nor pass over it; which must be owing to the almighty power and sovereign will of God, who has given the sea a decree that its waters should not pass his commandment; and it must be ascribed to his promise and oath that the waters no more go over the earth to destroy it; see Psalm 104:9, Proverbs 8:27; until the dark and night come to an end; that is, as long as there will be the vicissitudes of day and night, till time shall be no more, as long as the world stands; for the those shall constitute so long are the ordinances of God, which shall never depart, and the covenant he has made, which shall never become void; wherefore, as long as they remain, the sea and its waters will be bounded as not to overflow the earth, Genesis 8:22; or "until the end of light with darkness" (a); until both these have an end in the same form and manner they now have; otherwise, after the end of all things, there will be light in heaven, and darkness in hell. Aben Ezra interprets it thus,
"unto the place which is the end of light, for all that is above it is light, and below it the reverse;''
he seems to have respect to the place that divides the hemispheres, where when one is light the other is dark; and so others seem to understand it of such places or parts of the world as are half day and half night, and where one half of the year is light, and the other dark; but the first sense is best.
(a) "usque ad finem lucis cum tenebris", Cocceius, Michaelis; so Targum & Sept.

Rather, "He hath drawn a circular bound round the waters" (Proverbs 8:27; Psalm 104:9). The horizon seems a circle. Indication is given of the globular form of the earth.
until the day, &c.--to the confines of light and darkness. When the light falls on our horizon, the other hemisphere is dark. UMBREIT and MAURER translate "He has most perfectly (literally, to perfection) drawn the bound (taken from the first clause) between light and darkness" (compare Genesis 1:4, Genesis 1:6, Genesis 1:9): where the bounding of the light from darkness is similarly brought into proximity with the bounding of the waters.