John Calvin Commentary Galatians 4:13

"but ye know that because of an infirmity of the flesh I preached the gospel unto you the first time:" — Galatians 4:13 (ASV)

You know that, through infirmity of the flesh. He reminds them of the friendly and respectful way they had received him, and he does this for two reasons. First, to let them know that he loved them, and thus to gain a receptive hearing for all that he says; and secondly, to encourage them, so that, as they had begun well, they would continue in the same course. This mention of past occurrences, then, while it is an expression of his kind regards, is also intended as an exhortation to act in the same way they had done previously.

By infirmity of the flesh he means here, as in other places, what had a tendency to make him appear lowly and despised. Flesh denotes his outward appearance, which the word infirmity describes as contemptible. Such was Paul when he came among them, without show, without pretense, without worldly honors or rank, without everything that could gain him respect or esteem in the eyes of men. Yet all this did not prevent the Galatians from giving him the most honorable reception.

The narrative contributes powerfully to his argument, for what was there in Paul to awaken their esteem or veneration, but the power of the Holy Spirit alone? Under what pretext, then, will they now begin to despise that power? Next, they are charged with inconsistency, since no subsequent event in the life of Paul could entitle them to esteem him less than before. But this he leaves to be considered by the Galatians, contenting himself with indirectly suggesting it as a subject for consideration.