The event where Jesus "clears the temple" and drives out the merchants is thought by most people to have occurred during the last week of Jesus' life, although there's evidence that it may have actually happened more than once (for example, John tells of a temple-clearing incident occurring much earlier than the other Gospels indicate--see John 2).
In this familiar scene, Jesus became overcome by righteous indignation because the outer courtyard of the temple, meant to be a place for worship, had become a place for buying and selling, overrun by those seeking to make a profit rather than seeking God. So Jesus entered the temple and drove these people out, claiming, "It is written, 'My house will be called a house of prayer.'"
After dealing with the people who were keeping others from worship, Jesus turned his attention to the blind and the lame, healing them right there at the temple, while little children shouted, "Hosanna to the Son of David!" (Matthew 21:14-15).
When was the last time we were consumed by this sort of passion for what takes place in our churches, the modern-day equivalent of the temple--and, for that matter, in our homes? Are we passionate about making these places houses of prayer, worship, healing, and grace, as Jesus was? Are we willing to make these places ones where people can come with real needs and receive real compassion, as the blind and the lame did in Jesus' day? If not, why not? What's stopping us? Are their miracles that God wants to do through us in our modern-day "temples" that we won't be able to see because we're too focused on money, convenience, our own agendas, and everything else that can keep us from the Lord?
I think there may have been another reason that Jesus specifically chose to clear the temple at this time and to restore an attitude of prayerful worship there: because a miraculous event was soon to take place there. Just days later, at the moment Jesus breathed his last on the cross, the curtain inside the temple, surrounding the Most Holy Place, was torn in two from top to bottom--symbolizing that through Christ, people would have free access to God at any time, without needing a priest or any other mediator to go on their behalf. It seems that Jesus may well have wanted the temple cleared of distraction, of needless noise and commotion and activities that had nothing to do with worship, so that everyone there could bear witness to the ushering in of the new covenant, in which "we have confidence to enter the Most Holy Place by the blood of Jesus." (Hebrews 10:19) And this is an ongoing miracle that we can still bear witness to today--through Christ, all the barriers that keep us from a right relationship with God have been shattered, and we can step into the temple, even the Most Holy Place, with boldness.