John Calvin Commentary Luke 1:14

"And thou shalt have joy and gladness; and many shall rejoice at his birth." — Luke 1:14 (ASV)

He shall be to you 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 a son such as he had not even ventured to wish. He even proceeds further to state that the joy would not be domestic, enjoyed by the parents alone, or confined within private walls, but also shared by strangers, to whom the advantage of his birth was to 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 to introduce a profane custom in celebrating the birthday 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. Even the amusements authorized on that day are 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 birthday, 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.