Matthew 18:19

“Again I say to you, that if two of you shall agree on earth as touching anything that they shall ask, it shall be done for them of my Father who is in heaven.”

The question that arises here is as to whether this should be strictly applied in context, or seen as an expansion on the argument. In the former case it is confirmation that when a plurality (two or more) agree on what to ask about a disputed question, (‘about any judicial matter that they should ask') they can be sure that they will have His Father's assistance in the matter. He will give them guidance and show them what to do. This may be very necessary in the case of the two called on in Matthew 18:16.

In the latter case the argument is that just as two or three could act together to confirm a case before the congregation (Matthew 18:16), so equally two or more can confirm any request which is in accordance with Scripture which is to be made to His Father, with the result that they can be sure that they will receive what they ask. The idea of ‘two agreeing' is then not just a casual agreement to pray for something without due thought, but a coming together to first determine what would be reasonable to request. It is taking prayer seriously. They would thus take into account the principles of prayer, such as asking according to His known will (1 John 5:14), coming in the name of Jesus (asking what He wills, backed up by the authority of His Name), asking in accordance with Scripture promises, asking as those who have no iniquity in their hearts, and so on. Once, however, they had genuinely come to what they believed was the mind of God on the matter they could have confidence that they would receive what they asked. (The final judgment would come in whether the prayer was answered or not).

As with Matthew 18:18 probably both are true. Jesus intended it to have both the particular application, and the wider general application (as He makes clear elsewhere).