Paul calls Onesimus “my child, whose father I became in my imprisonment.” The wording indicates a close relationship formed while Paul was in chains (Philemon 1:10).
In Philemon 8–11 Paul says he could issue a strong instruction, but instead he chooses to ask. He frames his request “for love’s sake,” presenting himself as an older man and also as someone in prison, which adds weight without forcing the outcome. These verses begin the letter’s main request after Paul has already praised Philemon’s love and the comfort he brings to others (Philemon 4–7). Paul now turns from affirmation to persuasion: he sets up a contrast between what he has the standing to demand and what he chooses to do instead.
Paul presents himself as having real standing “in Christ” to tell Philemon what to do, yet he deliberately chooses not to use that leverage (verse 8). Instead, he frames his approach as an appeal “for love’s sake” (verse 9).
A common mistake is to turn the wording into a slogan. The better reading keeps the phrase tied to the passage, the speaker, and the problem the book is addressing.
Start with Philemon 1:10, then read the surrounding section so the answer stays connected to the passage's flow.
10I beg you for my child, whom I have fathered in my bonds, Onesimus,