The moneychangers were renting their spaces from the priests, said the Pope in a strong warning about the "Lord of Money."
"This is the lord that can ruin our life and can lead us to end our life in a bad way, without happiness, without the joy of serving the true Lord, who is the only one capable of giving us that true joy."
The Pope particularly focused on the dangers of the love of money in the priesthood. He said the people of God forgive "so many sins" by priests, except for attachment to money and mistreating people.
"Following the Lord of Money leads a priest to be the head of a firm or be a prince or we can go even higher," he warned the priests gathered for Mass. "It's sad to see a priest who's at the end of his life, he's in agony, he's in a coma and his relatives are there like vultures, looking to see what they can take away."
He recounted the story of Jacob's wife Rachel who kept hidden her idols, called teraphim. For Pope Francis, this is an image of attachment to material goods.
"Let us grant this pleasure to the Lord, a true examination of our conscience: 'Lord, are you my Lord or is it, like Rachel, these teraphim hidden in my heart, this idol of money?'"