Some critics isolate Matthew 18:19 from its context to present it as a general instruction on how to pray for whatever one wants. This misses the textual context.

This passage follows instructions for pursuing 'sheep' (members of the believing community) who go astray. Verses 15-18 are further instructions for community discipline. Verse 19 is an amplification on verse 18, using the 'Again, I say unto you' which indicates an expansion of what has been noted previously. Thus, whatever verse 19 means, it is restricted to the context of discipline within the believing community of Christ. It is not a license to request anything.

So then, in this context, what is this prayer for? Verse 18 refers to binding and loosing, a metaphor in this period for judicial authority. The word for 'thing' (pragma) is a term frequently limited to judicial matters. The reference to two agreeing mirrors the situation in a Jewish court representing the community in which two out of three witnesses agree. The action described in verse 17 is the disfellowship of an unrepentant sinner from the community of believers, something which in turn is recognized in Heaven. This is the only context for this instruction. It does not even have tangible, earthly results; it is an issue of status.