*Minor differences ignored. Grouped by changes, with first version listed as example.
Neither shalt thou swear by thy head - This was a common oath. The Gentiles also used this oath. To swear by the head was the same as to swear by the life; or to say, I will forfeit my life if what I say is not true. God is the Author of the life, and to swear by that, therefore, is the same as to swear by him.
Because thou canst not make one hair white or black - You have no control or right over your own life. You cannot even change one single hair. God has all that control; and it is therefore improper and profane to pledge what is God's gift and God's property; and it is the same as swearing by God himself.
Neither shalt thou swear by thy head - For these plain reasons:
1st. God commands thee not to do it.
2dly. Thou hast nothing which is thy own, and thou shouldst not pledge another's property.
3dly. It never did, and never can, answer any good purpose. And
4thly. Being a breach of the law of God, it is the way to everlasting misery.
Neither shalt thou swear by thy head,.... This also was a common form of swearing among the Jews: take a few instances.
"If anyone is bound to his friend by an oath, and says to him, vow unto me , "by the life of thy head"; R. Meir says (u), he may retract it; but the wise men say, he cannot.''
Again (w), a certain Rabbi said to Elijah,
"I heard "Bath Kol" (or the voice from heaven) mourning like a dove, and saying, woe to my children; for, because of their sins, I have destroyed my house, and have burnt my temple, and have carried them captive among the nations: and he (Elijah) said unto him , "by thy life, and by the life of thy head", not this time only it says so, but it says so three times every day.''
Once more (x), says R. Simeon ben Antipatras, to R. Joshua,
"I have heard from the mouth of the wise men, that he that vows in the law, and transgresses, is to be beaten with forty stripes: he replies, blessed art thou of God, that thou hast so done, , "by thy life, and by the life of thy head", he that is used to do so is to be beaten.''
This form of swearing is condemned, for this reason,
because thou canst not make one hair white or black: which shows, that a man's head, nor, indeed, one hair of his head, is in his own power, and therefore he ought not to swear by it; as he ought not to swear by heaven, or earth, or Jerusalem, because these were in the possession of God. Some copies read, "canst not make one white hair black".
(u) Misn. Sanhedrim, c. 3. sect 2. (w) T. Bab. Beracot, fol. 3. 1. (x) Derech. Eretz, c. 6. fol. 18. 2.
Neither shalt thou swear by thy head, because thou canst not make one hair white or black--In the other oaths specified, God's name was profaned quite as really as if His name had been uttered, because it was instantly suggested by the mention of His "throne," His "footstool," His "city." But in swearing by our own head and the like, the objection lies in their being "beyond our control," and therefore profanely assumed to have a stability which they have not.
By thy head. Senseless, since the oath could have no meaning. Dr. Thompson (The Land and the Book) says the Orientals are still terribly profane, swearing continually by the head, the beard, the heart, the temple, the church.
For thou canst not make one hair white or black - Whereby it appears, that this also is not thine but God's.
*More commentary available at chapter level.