Jesus taught about what we should do if someone sins against us and about agreeing when we pray.

Matthew 18:15-20

15 “If a fellow believer sins against you, go to him, and when you two are alone, reprove him for sinning against you. If that person listens to you and feels sorry that he has sinned against you, you will have restored your friendship with that person. 16 If that person will not listen to you nor feel sorry that he has sinned against you, go get one or two other people who will listen to what you both have to say. Have them go with you so that what is written {Moses wrote} in the Scriptures might happen: ‘When one person accuses another in some matter, it should be confirmed by at least two or three people {at least two or three people should confirm it} before that person can be declared guilty {before they declare that person guilty}.’ 17 If the one who has sinned against you will not listen to them or does not feel sorry that he has sinned against you, tell that to the congregation so that they can rebuke him. If that person will not listen to the congregation or feel sorry that he has sinned against you, exclude him from being a member of your congregation, just like you would exclude pagans, tax collectors, and others who do not believe in God and sin greatly. 18 Keep this in mind: Whatever you decide on earth about punishing or not punishing a member of your congregation is what has also been decided by God in heaven {what God in heaven has also decided}. 19 Also note this: If at least two of you who live here on earth agree together about something you ask God for [DOU], God, my Father who is in heaven, will give you what you ask for. 20 This is true, because wherever at least two or three of you assemble because you believe in me [MTY], I am spiritually present with you. I will hear what you ask for and I will ask God to do it for you.”