Philemon 1:10

‘I plead with you for my child, whom I have begotten in my bonds, Onesimus,’

And his plea is for Onesimus, to whom he sees himself as a father, because even while he was in prison he had won him to Christ with the result that Onesimus has been born of the Spirit. Here we have the evidence that in some way Onesimus came to him, for he was unable to go out teaching and preaching.