Leviticus 19:17
15 “‘You must not deal unjustly in judgment: You must neither show partiality to the poor nor honor the rich. You must judge your fellow citizen fairly. 16 You must not go about as a slanderer among your people. You must not stand idly by when your neighbor’s life is at stake. I am the Lord. 17 You must not hate your brother in your heart. You must surely reprove your fellow citizen so that you do not incur sin on account of him. 18 You must not take vengeance or bear a grudge against any of your people, but you must love your neighbor as yourself. I am the Lord. 19 You must keep my statutes. You must not allow two different kinds of your animals to breed together, you must not sow your field with two different kinds of seed, and you must not wear a garment made of two different kinds of material.
Matthew 18:15
14 In the same way, your Father in heaven is not willing that one of these little ones be lost. 15 “If your brother sins, go and show him his fault when the two of you are alone. If he listens to you, you have regained your brother. 16 But if he does not listen, take one or two others with you, so that at the testimony of two or three witnesses every matter may be established. 17 If he refuses to listen to them, tell it to the church. If he refuses to listen to the church, treat him like a Gentile or a tax collector. 18 “I tell you the truth, whatever you bind on earth will have been bound in heaven, and whatever you release on earth will have been released in heaven. 19 Again, I tell you the truth, if two of you on earth agree about whatever you ask, my Father in heaven will do it for you.
Notes and References
"... Evidently the community at Qumran interpreted the imperative, 'you shall reprove your neighbor, or you will incur guilt yourself' (Leviticus 19:17), to mean that if you see another commit some sin, it is your duty, in order to avoid guilt, to reprove that person. The reproof is to be undertaken in the presence of witnesses. But if that fails, the matter must be taken up before 'the Many,' that is, the elders or some official body of the community. We may now return finally to Matthew 18:15-18. Obviously behind it lies a Jewish tradition of rebuke based upon Leviticus 19:17-18. This important fact is bound to escape the modern reader, who will miss the allusion to that famous Pentateuchal text ..."
Allison, Dale C. Scriptural Allusions in the New Testament: Light from the Dead Sea Scrolls (p. 27) Wipf & Stock Publishers, 2019