Jesus teaches forgiveness in Mathew 18: 21. But he does just the opposite when he drives out people from the temple (John 2: 15). Why is it?

Thank you for this question – and it really is interesting! It seems rather strange that Jesus who was almost always gentle and merciful was angry and even used physical force to drive out the cattle and money changers and overturned the tables. If we tease out the question you asked a little more there are two aspects to consider: forgiveness and anger. Since very often in our ordinary experience unforgiveness leads to anger, we might assume that if there is anger there must be unforgiveness. Although they often go together, they are actually two different things and not the same. For instance, one can have unforgiveness and be utterly cold and cut off someone from their lives without being hot with anger. 

Thinking about anger a little bit more, of course from knowing our own anger and the experience of anger from other people we know that it is always tainted with hatred, unforgiveness or impatience. But anger itself is not bad, in fact, righteous anger is necessary and important. For instance, if one were to see innocent people being abused and treated horribly and not feel anger – there would be something very wrong with that person. On the other hand feeling angry because someone made a small offense that hurt one’s ego is hardly the same. So there is righteous anger and there is selfish anger: and for the most part we mostly feel the second. Aristotle said: “Anybody can become angry — that is easy, but to be angry with the right person and to the right degree and at the right time and for the right purpose, and in the right way — that is not within everybody’s power and is not easy.” A positive example of anger we might have seen or at least can imagine would be a gentle father who is very patient and loves his son very much, but the son plays with fire despite being spoken to many times and warned. The father does not hate or despise the son in the least but becomes angry at seeing this not from unforgiveness but from the abundance of love.

So now let us turn back to Jesus as He cleanses the Temple: is His anger self-serving or selfish in anyway? Is it out of hatred and unforgiveness or is it out of love? The Temple in Jerusalem had pride of place in Jewish life and faith: it was the longing of a people across many generations to offer prayers and sacrifices there. The Temple had “layers” the Holy of Holy where the high priest entered only once a year, the part where the Jews alone entered and prayed and the courtyard which was meant for gentiles so that there was a physical reminder that all people would one day worship the same God. In this place reserved for the promise of God for all people to the one, true God there were people bringing in all sorts of animals for the sacrifices and buying selling them. Even though the animals were for the sacrifice in the temple, the objective was shifted to the exchange of money (the sign of worldly cares and pleasures, of faith in man rather than God) and also taking up the space for the promise of God with no care for the actual Temple. So it is no wonder that John says that “zeal for (God’s) house consumed” Jesus. (John 2:17) It would be strange if the Son of God became incarnate and went to the house dedicated to the Heavenly Father as a sacred place for prayer and sacrifice and saw a chaotic market and did not get angry! But just like the anger of the father mentioned before, this anger was not to harm or condemn anyone but it was to help show the issue at hand. Later in John 16:18, Jesus says that when He leaves He will send the Holy Spirit to convict us of sin…so that we may repent and then receive His forgiveness.

So the cleansing of the Temple is not opposed to forgiveness, but is actually the first step towards the people recognizing sin, repenting and then receiving Jesus’ mercy which He would give without holding anything back on the Cross, including the moneychangers.