18 “Assuredly, I say to you, whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven.
19 “Again I say to you that if two of you agree on earth concerning anything that they ask, it will be done for them by My Father in heaven.
20 For where two or three are gathered together in My name, I am there in the midst of them.”
The instructions given to Peter in Matthew 16:19 are here given to all the apostles. See my notes on that passage for an explanation of this verse. In the immediate context, it is applied to the matter of dealing with a sinning member of the assembly.
in My name (v.20) — claiming and using Christ’s authority
The Lord was not talking about the church here. He was talking about the kingdom (vs. 1, 3-4). And He was not speaking to all believers, but to the disciples (v.1). But the principles of forgiveness and dealing with sinning brothers can be applied today.