Adam Clarke Bible Commentary

Thou art not yet fifty years old - Some MSS. read forty. The age of our blessed Lord has never been properly determined. Some of the primitive fathers believed that he was fifty years old when he was crucified; but their foundation, which is no other than these words of the Jews, is but a very uncertain one. Calmet thinks that our Lord was at this time about thirty-four years and ten months old, and that he was crucified about the middle of his thirty-sixth year; and asserts that the vulgar era is three years too late. On the other hand, some allow him to have been but thirty-one years old, and that his ministry had lasted but one year. Many opinions on this subject, which are scarcely worthy of being copied, may be found in Calmet.