He shall be to thee joy The angel describes a greater joy than what Zacharias could derive from the recent birth of a child; for he informs him that he would have such a son as he had not even ventured to wish. He even proceeds farther to state that the joy would not be domestic, enjoyed by the parents alone, or confined within private walls, but shared alike by strangers, to whom the advantage of his birth should be made known. It is as if the angel had said that a son would be born not to Zacharias alone, but would be the Teacher and Prophet of the whole people. The Papists have abused this passage for the purpose of introducing a profane custom in celebrating the birth-day of John. I pass over the disorderly scene of a procession accompanied by dancing and leaping, and licentiousness of every description, strangely enough employed in observing a day which they pretend to hold sacred, and even the amusements authorized on that day taken from magical arts and diabolical tricks, closely resembling the mysteries of the goddess Ceres. It is enough for me, at present, to show briefly that they absurdly torture the words of the angel to mean the annual joy of a birth-day, while the angel restricts his commendation to that joy which all godly persons would derive from the advantage of his instruction. They rejoiced that a prophet was born to them, by whose ministry they were led to the hope of salvation,

Many shall rejoice at his birth - This does not refer so much to the time of his birth as to the subsequent rejoicing. Such will be his "character," that he will be an honor to the family, and many will rejoice that he lived: or, in other words, he will be a blessing to mankind.

Thou shalt have joy, etc. - ΕϚαι χαρα σοι, He will be joy and gladness to thee. A child of prayer and faith is likely to be a source of comfort to his parents. Were proper attention paid to this point, there would be fewer disobedient children in the world; and the number of broken-hearted parents would be lessened. But what can be expected from the majority of matrimonial connections, connections begun without the fear of God, and carried on without his love.
Many shall rejoice at his birth - He shall be the minister of God for good to multitudes, who shall, through his preaching, be turned from the error of their ways, and converted to God their Savior.

And thou shalt have joy and gladness,.... Not only because of his having a son; but because this his son would be the prophet of the Highest; would go before the Lord, and prepare his ways; give knowledge of salvation to many, and light to them that were in darkness, and guide their feet in the way of peace: all which, and more, he afterwards expresses in his song, whereby this part of the angel's prediction had its accomplishment:
and many shall rejoice at his birth; as the neighbours and cousins of his parents did; see Luke 1:58 and not only they, but all others, who, afterwards had knowledge of him as prophet, and as the forerunner of the Messiah.

shall rejoice--so they did (Luke 1:58, Luke 1:66); but the meaning rather is, "shall have cause to rejoice"--it would prove to many a joyful event.