I would think you are talking about another follwer of Christ and are referring to these scriptures:
Matthew 18:15 'If a brother or sister sins, go and point out the fault, just between the two of you. If they listen to you, you have won them over. 16 But if they will not listen, take one or two others along, so that “every matter may be established by the testimony of two or three witnesses.” 17 If they still refuse to listen, tell it to the church; and if they refuse to listen even to the church, treat them as you would a pagan or a tax collector. 18 'Truly I tell you, whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven.
Galatians 6:1 Brothers, if someone is caught in a sin, you who are spiritual should restore him gently. But watch yourself, or you also may be tempted
The best way to minister in this area is to first be walking with a pure heart before the Lord and take it to prayer.
II Timothy 3:16 tells us All Scripture is inspired by God and profitable for teaching, for reproof, for correction, for training in righteousness. This is your guide as you share the word of the Lord…Be aware of the situation and be sensitive to the Spirit’s working.
Always operate out of love…Be gentle…Don’t sharply rebuke someone who is your
elder…May the Lord guide and direct you as you minister in this situation…