John Calvin Commentary Galatians 1:13

"For ye have heard of my manner of life in time past in the Jews` religion, how that beyond measure I persecuted the church of God, and made havoc of it:" — Galatians 1:13 (ASV)

For you have heard of my conversation. The whole of this narrative was added as a part of his argument. He relates that, during his whole life, he had such an abhorrence of the gospel that he was a mortal enemy of it and a destroyer of the name of Christianity. Hence we infer that his conversion was divine. And indeed, he calls them as witnesses of a matter not at all doubtful, so as to place beyond controversy what he is about to say.

His equals were those of his own age; for a comparison with older persons would have been unsuitable. When he speaks of the traditions of the fathers, he means not those additions by which the law of God had been corrupted, but the law of God itself, in which he had been educated from his childhood and which he had received through the hands of his parents and ancestors. Having been strongly attached to the customs of his fathers, it would have been no easy matter to tear him from them if the Lord had not drawn him by a miracle.