I said unto them, It is written, My heart shall be called the house of prayer, but thou hath made it the den of theives.
This was quoting the scripture that where the people turned the temple into a marketplace where so many buying and selling were going on. which was not favourable at all. Whenever he said these things, we then respect to know what the scripture is saying.
There are people who will turn the house of prayer of God into the den of thieves and all kinds of manner of things, doing all kinds of evil things in the house of God. Even before it was said by the Lord Jesus Christ, it was prophesied by Jesus.
Even in the Bible, my house shall be called the house of prayer. But He has made it a den of thieves. The house of prayer in Jerusalem was where den of thieves were staying and it was not acceptable at all in the house of God.
God wants us to be scared and not use his temple for where illegal activities should be going on or things offered by businessmen. In time of Jesus can make the house of prayer.
In the time of the lord Jesus Christ he said that apostle that the temple will be totally destroyed. Which that place is the house of prayer. Jesus said to the apostle that that particular temple is called the house prayer will be destroyed and it will return to a new place.