Philemon 1:9 You owe me one.
This letter epistle has a wonderful lesson to teach. Somehow Onesimus and Paul had come together and Paul had led him to Christ, ("I have begotten"). Was he a fellow prisoner? I think we must assume that he was, but that he was in for a short sentence because (v.12) Paul sends him back to Philemon who for some reason would think of him as an unprofitable servant (v.11). Perhaps, as some commentators suggest, he had stolen from Philemon and for that, had been incarcerated. We do not know these details.
What we do know is that now, being saved, he had become important to Paul (v.13) and though he would have likes to have retained him, he deemed it best to send him home to be reunited with his master.
How could Philemon resist Paul's plea on behalf of this young man? Receive him as a brother (v.16). Receive him as if it were me coming to see you(v.17). Put what he owes on my account(v.18). But, remember what you owe me--perhaps this may help to even the score (v.19). He ministered to me in your place (v.13).
This story provides us with an example of what is meant by the term in Romans 6:11 "reckon." (Translated 6 times as such in the A.V,---8 times as "impute"). Here Paul tells him to put what Onesimus owes Philemon on his account thus erasing what he owed (the soul that sins must die). If Philemon would weigh what Paul had done for him against what Onesimus had done for him, there could be no debt owed.
Further study of this verse can be found in Romans 4. Note the words: "counted" (v.5); "reckoned" (v.9); "imputed"(v.23), as examples found throughout. Also Gal.3:6. In the Greek these words come from the same root. When we understand the meaning of these words in relation to what Christ has done for us, we understand the basis of our position in Christ.