“It is written, ‘My house will be called a house of prayer’ ...'" (Matthew 21:13)

Jesus entered the temple courts and drove out all who were buying and selling there. He overturned the tables of the money changers and the benches of those selling doves. "It is written," he said to them, " 'My house will be called a house of prayer,' but you are making it 'a den of robbers.'" (Matt 21:12-13)

Why did Jesus overturn the tables?

Jesus goes to Jerusalem and enters a temple court, where he saw many people conducting a marketplace on the temple grounds, where they were selling everything from sheep and cattle to doves. He looks at the marketplace and begins turning over the tables.

Jesus did not condone having a market and doing business in a place that was supposed to be a place for worshiping God.

In the Book of John it describes that Jesus also ‘made a whip out of cords, and drove all from the temple area, both sheep and cattle; he scattered the coins of the money changers and overturned their tables. To those who sold doves he said, “Get these out of here!...”’ (John 2:15-16)

Jesus was obviously upset. To drive out people and overturn tables and benches displays an intensity that contrasts with the notion of being a peacemaker, or turning the other cheek, or not defending himself being accused falsely.

Jesus was angry.

Why was Jesus so angry?

The anger that Jesus displayed arose out of his love for God.

Jesus cared about how people were treating his Beloved's place of worship. Instead of honoring God and focusing on God within His temple, these people were using the temple for their own purposes.

They were using the temple in order to become wealthier. They could have easily set up their marketplace outside of the temple grounds. Instead, they used the temple grounds because this was a place that most of the people went to worship.

They were using the temple grounds to get more proximity to the people in order to make more money. Instead of using the temple for the purpose it was built for - to worship God - they were abusing the temple for their own purposes.

This made Jesus angry because he loved God. Just as someone would be upset if someone was abusing their wife or friend, Jesus was upset because they were abusing the temple - thus abusing God.

What did Jesus mean by 'a house of prayer'?

Jesus is quoting from two elements within the scriptures:
[This is what the Lord says,] “these I will bring to My holy mountain and give them joy in My house of prayer. Their burnt offerings and sacrifices will be accepted on My altar; for My house will be called a house of prayer for all nations.” (Isaiah 56:7)
And
“Has this house, which bears my Name, become a den of robbers to you? But I have been watching!” declares the LORD. (Jeremiah 7:11)
These statements are both spoken by God directly or through His representative. Jesus was obviously very educated in the scriptures, as he was able to draw from two different books of scripture at the same time - drawing upon statements that God made about His temple of worship.

What does this say about Jesus?

Jesus' statement also illustrates how focused Jesus was on the Supreme Being. He was not simply quoting passages from scripture to look good in front of a congregation. He was focused upon the words of God and their application towards actions that are pleasing to the Supreme Being.

Jesus' actions also illustrated his devotion to a personal God. He knew what pleases God and displeases God. He knew that God is personally displeased when we utilize His place of worship for other purposes other than to honor and worship Him. Why?

Because God knows that if we re-establish our relationship with Him, we will be happy. It's all about love.

What about having markets and bazaars on church grounds today?

This event and its application is still important today. So many churches, temples, mosques and synagogues throughout the organized religions of the world are being used as places to hold political assemblies, bazaars, flea markets, sporting events and so many other activities. Is this the same thing?

It is the same thing. Using a place of worship in order to make money or otherwise promote concerns outside of worshipping God would be an abuse of that place of worship.

In these cases, once again the place of worship is being used because is it a well-recognized center for people to come. They normally come to worship there. So using it for another purpose would effectively be using people's place of worship to promote an outside concern.

Thus, using God's place of worship for such activities was condemned by Jesus then, and now.

Aren't they good gathering places?

Many will say that churches, temples, synagogues or mosques are good gathering places because they bring people together. But is this the intended purpose of the church, temple, mosque or synagogue?

As we can see clearly by God's statements in Isaiah and Jeremiah, no.

The purpose of these buildings is to foster our remembrance and our dedication to the Supreme Being. Traditionally, they were also built with altars to God, in order to make offerings to God.

To utilize the buildings and grounds for any other purpose is to offend God and desecrate their very purpose.

Places of worship are meant to be used solely to focus our hearts and minds upon our Soul Mate the Supreme Being: To sing God's Names, pray to God, make offerings to God and teach about God. Jesus himself makes this point very clear here, and this is consistent with his primary instruction:
“ ‘Love the Lord your God with all your heart and with all your soul and with all your mind.' This is the first and greatest commandment.” (Matthew 22:37-38)