18:15 Both "ifs" here, as in "if a brother sins," and "if he listens to you" are completely hypothetical, meaning this may or may not happen.
The word gain here (kerdain-oo) is the same as in last week's reading -- what will it benefit him if he gains the world...
-The NRSV imports the word "member" into this verse here; there is no such word in the Greek text.
-The word for Gentile is literally "ethnic"
18:18 Both verbs relating to sins -- binding and loosing -- are in the perfect, meaning the deed in complete.
18:19 The word here that the NRSV uses for "agree" is acutally "symphone-oo" So, literally, if there is a symphony, it will be done.
18:20 Every other verse in this section has an "if" clause; here Jesus simply declares -- Where two or three are gathered, I am in the midst of you. Also, the word for gathered (synago) is in the perfect passive, hinting that it is not we who gather, but God who has already gathered us. Thus, we move from human action to God's promise. Also worth noting that Jesus promises his presence in the midst of the office of the keys and congregational conflict.