4:13-16 What was Paul's infirmity of his flesh and his temptation which he refers to here?

Many Christians in the contemporary church believe that Paul's infirmity of the flesh to which he refers here was a chronic illness, but that is not correct.

It was his physical appearance after his near-death stoning which happened in Lystra soon after he and Barnabas took the gospel to Galatia on his first apostolic mission journey (cp Ac 13:1-3; 14:1-20).

The expression my temptation which was in my flesh (in Ga 4:14) referred to Paul's test of faith - the stoning - which he had just endured. His physical appearance was repulsive yet the Galatians did not despise nor reject him, but received him as they would Jesus himself.

The stoning Paul received was one of "the marks of the Lord Jesus" he bore in his body (cp Ga 6:17 with 2Cor 11:23-27 and 2Ti 3:10-11).

Some in the church use Ga 4:15 to prove that Paul had an eye disease that made him hideous to look upon.

But what Paul is simply saying in effect is that despite how repulsive he looked when he first witnessed to the Galatians they were so sympathetic to his suffering that they would have plucked their eyes out and given them to him if they could have done so.

(This is no more sinister than saying that they would have given their right arm or leg to help him too, if they could have done so.)

Paul then goes on to wonder in V 16 if their affections have changed toward him because he always told them the truth (cp Ga 4:15-16).