From: Luke 19:45-48
Jesus in the Temple
 And He (Jesus) entered the temple and began to drive out those who sold,  saying to them, "It is written, `My house shall be a house of prayer'; but you have made it a den of robbers."
 And He was teaching daily in the temple. The chief priests and the scribes and the principal men of the people sought to destroy Him;  but they did not find anything they could do, for all the people hung upon His words.
45-48. Jesus' indignation shows His zeal for the glory of His Father, to be recognized at this time in the temple itself. He inveighs against the traders for engaging in business which has nothing to do with divine worship (cf. Matthew 21:12; Mark 11-15). Even the priests allowed some of these abuses to go on--perhaps because they benefited from them in the form of taxes. The traders did perform services necessary for divine worship but this was vitiated by their excessive desire for gain, turning the temple into a marketplace.
"My house shall be a house of prayer": Jesus uses these words from Isaiah (56:7; cf. Jeremiah 7:11) to underline the purpose of the temple. Jesus' behavior shows the respect the Temple of Jerusalem deserved; how much more reverence should be shown our churches, where Jesus Himself is really present in the Blessed Sacrament. (cf. notes on Matthew 21:12-13; and Mark 11:15-18).
[The notes on Matthew 21:12-13 states:
12-13. Although God is present everywhere and cannot be confined within the walls of temples built by man (Acts 17:24-25), God instructed Moses to build a tabernacle where He would dwell among the Israelites (Exodus 25:40). Once the Jewish people were established in Palestine, King Solomon, also in obedience to a divine instruction, built the temple of Jerusalem (1 Kings 6-8), where people went to render public worship to God (Deuteronomy 12).
Exodus (23:15) commanded the Israelites not to enter the temple empty-handed, but to bring some victim to be sacrificed. To make this easier for people who had to travel a certain distance, a veritable market developed in the temple courtyards with animals being bought and sold for sacrificial purposes. Originally this may have made sense, but seemingly as time went on commercial gain became the dominant purpose of this buying and selling of victims; probably the priests themselves and temple servants benefited from this trade or even operated it. The net result was that the temple looked more like a livestock mart than a place for meeting God.
Moved by zeal for His Father's house (John 2:17), Jesus cannot tolerate this deplorable abuse and in holy anger He ejects everyone--to show people the respect and reverence due to the temple as a holy place. We should show much greater respect in the Christian temple--the Christian churches--where the eucharistic sacrifice is celebrated and where Jesus Christ, God and Man, is really and truly present, reserved in the tabernacle. For a Christian, proper dress, liturgical gestures and postures, genuflections and reverence to the tabernacle, etc. are expressions of the respect due to the Lord in His temple.
[The notes on Mark 11:15-18 states:
15-18. Our Lord does not abide lack of faith or piety in things to do with the worship of God. If He acts so vigorously to defend the temple of the Old Law, it indicates how we should truly conduct ourselves in the Christian temple, where He is really and truly present in the Blessed Eucharist. "Piety has its own good manners. Learn them. It's a shame to see those `pious' people who don't know how to attend Mass--even though they go daily,--nor how to bless themselves (they throw their hands about in the weirdest fashion), nor how to bend the knee before the Tabernacle (their ridiculous genuflections seem a mockery), nor how to bow their heads reverently before a picture of our Lady" ([St] J. Escriva, "The Way", 541).]
Source: "The Navarre Bible: Text and Commentaries". Biblical text taken from the Revised Standard Version and New Vulgate. Commentaries made by members of the Faculty of Theology of the University of Navarre, Spain. Published by Four Courts Press, Kill Lane, Blackrock, Co. Dublin, Ireland. Reprinted with permission from Four Courts Press and Scepter Publishers, the U.S. publisher.