The temple in Jerusalem is referred as house of prayer where Jesus usually go to worship and pray to God. This house is supposed to be a sacred place where the people of God will come to pray, ask for forgiveness of sins and tell God there problems through prayer. However, over time, religious leaders allowed commercial activities to take over the temple courts.
Many marketers came to the temple and turn their to a market, exploiting pilgrims who had traveled long distances. Instead of helping people draw near to God, the system began to take advantage of them, placing profit above prayer.
“My house shall be called a house of prayer, but you have made it a den of thieves” (Matthew 21:13).
Jesus wasn't happy when he got to the temple and saw how they have turned it from temple to market place. The temple leaders had maintained an appearance of religion while neglecting justice, mercy, and true devotion. The house of prayer became a den of thieves because the hearts of the people, especially the leaders, had turned from God. Their worship became outward and commercialized, rather than sincere and holy, which grieved God and brought Christ’s righteous anger.