John Calvin on Galatians 1:22

22. And was unknown by face. This appears to be added for the sake of shewing more strongly the wickedness and malignity of his slanderers. If the churches of Judea who had only heard respecting him, were led to give glory to God for the astonishing change which he had wrought in Paul, how disgraceful was it that those who had beheld the fruits of his amazing labors should not have acted a similar part! If the mere report was enough for the former, why did not the facts before their eyes satisfy the latter?