by Moody Adams Jesus in Matthew spoke; “And said unto them, It is written , My house shall be called the house of prayer; but ye have made it a den of thieves" (Matthew 21:13).
The place where Christians assemble is to be called a “house of prayer.” This instruction is found in the Old Testament, as well as the New: “Even them will I bring to my holy mountain, and make them joyful in my house of prayer: their burnt offerings and their sacrifices shall be accepted upon mine altar; for mine house shall be called an house of prayer for all people” (Isaiah 56:7).
When Christians gathered to worship outdoors, by a river, it was called a place 'where prayer was to be made': “And on the sabbath we went out of the city by a river side, where prayer was wont to be made ; and we sat down, and spake unto the women which resorted thither” (Acts 13:13).
If the building is a place for Christians to gather, we are instructed to call it a “house of prayer.” The command is followed by a rebuke. Their house of prayer had become a “den of thieves:” “Is this house, which is called by my name, become a den of robbers in your eyes? Behold, even I have seen it, saith the LORD” (Jeremiah 7:11).