A.T. Robertson Commentary Philemon 1:12

"whom I have sent back to thee in his own person, that is, my very heart:" — Philemon 1:12 (ASV)

I have sent back (ανεπεμψα). Epistolary aorist. As it will look when Onesimus arrives.

In his own person (αυτον). "Himself," intensive pronoun with ον (whom).

My very heart (τα εμα σπλαγχνα). As in verse 7. He almost loves Onesimus as his own son.