“If your brother sins
Against you,
Go!
Point out the fault,
When the two of you
Are alone.
If he listens to you,
You have regained
Your brother.”
Ἐὰν δὲ ἁμαρτήσῃ ὁ ἀδελφός σου, ὕπαγε ἔλεγξον αὐτὸν μεταξὺ σοῦ καὶ αὐτοῦ μόνου. ἐάν σου ἀκούσῃ, ἐκέρδησας τὸν ἀδελφόν σου·
This saying about the sinning brother has something similar in Luke, chapter 17:3, with some minor changes because Luke wanted the one offended to forgive the original offense. Jesus said that if one of your brothers has sinned against you (Ἐὰν δὲ ἁμαρτήσῃ ὁ ἀδελφός σου), point out that fault or rebuke him (ὕπαγε ἔλεγξον αὐτὸν), when the two of you are alone (μεταξὺ σοῦ καὶ αὐτοῦ μόνου). If he listens to you (ἐάν σου ἀκούσῃ), you have regained your brother (ἐκέρδησας τὸν ἀδελφόν σου). There was no mention of any forgiveness here. Is this a blood brother or a fellow disciple of Jesus brother? It appears to be a fellow follower of Jesus.
Eugene Finnegan Bible Project 