Them refers to the people who were buying and selling and to the moneychangers, not just these latter ones. “He said to all those people” will make this clear.

It is written translates the same formula used at 4.4 (see comment there). “That God said” (Die Bibel im heutigen Deutsch “that God explained”) is included by Good News Translation in order to indicate the speaker referred to by the pronoun My of the quotation.

My house refers to the Temple, the place where God was said to dwell and where people worshiped him. Some translators have said “My house of worship” or “The house where people worship me.”

Shall be called a house of prayer is more adequately rendered by Bibel im heutigen Deutsch, 1st edition as “should be a house for prayer.” One may translate “should be a house where people come to pray to me,” or if prayer is understood in the wider sense of worship, “should be a house where people come to worship me.” Some translators have wanted to retain an element of called by saying “People will call my house a place for prayer” or “Regarding my Temple, people will know (or, say) that it is for worship.” But the passive shall be called does serve to keep My house in focus, and therefore examples like these should only be used if they maintain that focus. The quotation is taken from Isaiah 56.7, but Matthew omits “for the people of all nations,” which is important to Mark (11.17).

When Jesus says but you, he is addressing the moneychangers and merchants directly. He is no longer quoting from God’s Word.

A den of robbers (New American Bible “a den of thieves”) is a fairly traditional rendering. Den is literally “cave”; it was customary in those days for thieves and robbers to use caves as a place for their hideout and as a place for storing their stolen goods. Some translators have understood den to mean a gathering place for robbers, but in fact it was a place where they could hide (possibly after committing a crime) and be safe, so that “hiding place” is a better translation. Jesus is here alluding to Jeremiah 7.11: “Do you think that my Temple is a hiding place for robbers?” (TEV).

Quoted with permission from Newman, Barclay M. and Stine, Philip C. A Handbook on the Gospel of Matthew. (UBS Handbook Series). New York: UBS, 1988. For this and other handbooks for translators see here .