If thou bring thy gift to the altar, and there rememberest that thy brother hath aught against thee;

Leave there thy gift before the altar, and go thy way; first be reconciled to thy brother, and then come and offer thy gift. Agree with thine adversary ... whiles thou art in the way with him; lest ... the adversary deliver thee to the judge, and the judge deliver thee to the officer, and thou be cast into prison. Verily I say unto you, Thou shalt by no means come out thence, till thou hast paid the uttermost farthing. Matt. v 23-26.

To be reconciled to a brother is to shun enmity, hatred and revenge; and it is clear that it is to shun it as a sin. The Lord also teaches in Matthew:

All things whatsoever ye would that men should do to you, do ye even so to them: for this is the Law and the Prophets. Matt. vii 12.

Thus, you should not do evil. He teaches this frequently in other places. The Lord also teaches that to kill means to be angry with a brother or a neighbour without a cause, and to account him an enemy. Matt. v 21, 22.