Matthew 6:1-18.

Lots of practical instructions here regarding how to worship, but the biggest point is to worship sincerely. When we pray, when we fast, and when we give we are to make sure that we are doing it for God, and not to be seen by others. That means when we do things like pray in a public setting, while we may say things in a different way because of where we are, in our hearts we are supposed to be praying to God.