Seemingly the following is the offending passage:
“Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them. For truly, I say to you, until heaven and earth pass away, not an iota, not a dot, will pass from the Law until all is accomplished. Therefore whoever relaxes one of the least of these commandments and teaches others to do the same will be called least in the kingdom of heaven, but whoever does them and teaches them will be called great in the kingdom of heaven. For I tell you, unless your righteousness exceeds that of the scribes and Pharisees, you will never enter the kingdom of heaven. You have heard that it was said to those of old, ‘You shall not murder; and whoever murders will be liable to judgment.’ But I say to you that everyone who is angry with his brother will be liable to judgment; whoever insults his brother will be liable to the council; and whoever says, ‘You fool!’ will be liable to the hell of fire." (Matt 5:17-22 ESV)
The first thing to understand is that “the Law and the Prophets” refers to the five books of Moses and the Old Testament prophets such as Isaiah and Jeremiah. Jesus said that the Scriptures spoke of Him (John 5:39). So Jesus came to fulfill the prophecies which spoke of Him. Not an iota or dot will pass from the Law until Jesus accomplishes all that was predicted concerning Him.
Now some think the next verse “relaxing one of the least of these commandments” is speaking of the Hebrew laws which Moses gave them. I say not.
Rather I affirm that He is speaking of His own commandments which He gave in Matthew 5, 6, and 7. Some of His commandments contrasted with the laws of Moses and others went even deeper than the laws of Moses. Jesus then gives examples of His commandments compared to the laws of Moses.
Notice that Jesus didn’t even say that the laws of Moses came from God, but rather, “You have heard that it was said to those of old”.
The first example is one of the ten commandments, “You shall do no murder.” But Jesus says that everyone who is angry with his brother is in liable to judgment. In other words, such a person is really a murderer at heart. The Mosaic commandment was to get revenge, “An eye for an eye and a tooth for a tooth”, but Jesus’ command was not to resist and evil person. If someone striked you on the cheek, turn the other and let him strike that one, too.
The fact is, Jesus NEVER committed any atrocity! He was never known to kill anyone, or command his disciples to kill anyone (quite unlike the OT standards in which God supposedly commanded the Israelites to kill and destroy).