He speaks to the people in the temple, and especially to the leaders who have responsibility.
He is teaching them, giving them education and explaining the meaning of what he has done. He makes the meaning of his act clear from the Scriptures. He is not a rebel against the temple and the authority of the scribes and priests, but he is the Teacher who explains God’s Word and applies it.
17 And he was teaching them and saying to them, “Is it not written, ‘My house shall be called a house of prayer for all the nations’? But you have made it a den of robbers.”