Albert Barnes Commentary Philemon 1:8

"Wherefore, though I have all boldness in Christ to enjoin thee that which is befitting," — Philemon 1:8 (ASV)

Wherefore, though I might be much bold in Christ. Though I might have much boldness as an apostle of Christ. He means that he was invested with authority by the Lord Jesus and would have a right, as an apostle, to command what should be done in the case which he is about to present to him. (Compare 1 Thessalonians 2:6–7).

To enjoin thee that which is convenient. This means to command what is proper to do. The word convenient here, (to anhkon,) means that which would be fit or proper in the case. .

The apostle implies here that what he was about to ask was proper to do in the circumstances, but he does not put it on that ground, but rather asks it as a personal favor. It is usually not best to command a thing to be done, if we can secure it just as well by asking for it as a favor. (Compare Daniel 1:8, 11-12).