4 What follows upon this? “And the Jews' passover was at hand; and He went up to Jerusalem.” The narrator relates another matter, as it came to his recollection. “And He found in the temple those that sold oxen, and sheep, and doves, and the changers of money sitting: and when He had made, as it were, a scourge of small cords, He drove them all out of the temple; the oxen likewise, and the sheep; and poured out the changers' money, and overthrew the tables; and said unto them that sold doves, Take these things hence; and make not my Father's house a house of merchandise.”
What have we heard, brethren? See, that temple was still a figure, and yet the Lord cast out of it all that sought their own, all who had come to market. And what did they sell there? Things which people needed in the sacrifices of that time. For you know, beloved, that sacrifices were given to that people, in consideration of the carnal mind and stony heart yet in them, to keep them from falling away to idols: and they offered there for sacrifices oxen, sheep, and doves: you know this, for you have read it.
It was not a great sin, then, if they sold in the temple that which was bought for the purpose of offering in the temple: and yet He cast them out thence. If, while they were selling what was lawful and not against justice (for it is not unlawful to sell what it is honorable to buy), He nevertheless drove those men out, and suffered not the house of prayer to be made a house of merchandise; how, if He found drunkards there, what would the Lord do? If the house of God ought not to be made a house of trading, ought it to be made a house of drinking?
But when we say this, they gnash upon us with their teeth; but the psalm which you have heard comforts us: “They gnashed upon me with their teeth.” Yet we know how we may be cured, although the strokes of the lash are multiplied on Christ, for His word is made to bear the scourge: “The scourges,” says He, “were gathered together against me, and they knew not.” He was scourged by the scourges of the Jews; He is now scourged by the blasphemies of false Christians: they multiply scourges for their Lord, and know it not. Let us, so far as He aids us, do as the psalmist did: “But as for me, when they were troublesome to me, I put on sackcloth, and humbled my soul with fasting.”
Source: Tractates on the Gospel of John (New Advent)