And it came to pass in those days, when Moses was grown up, that he went out unto his brethren, and looked on their burdens: and he saw an Egyptian smiting a Hebrew, one of his brethren. And he looked this way and that way, and when he saw that there was no man, he smote the Egyptian, and hid him in the sand. And he went out the second day, and, behold, two men of the Hebrews were striving together: and he said to him that did the wrong, Wherefore smitest thou thy fellow? And he said, Who made thee a prince and a judge over us? Thinkest thou to kill me, as thou killedst the Egyptian? And Moses feared, and said, Surely the thing is known.
Exodus 2:11-14

Well, one would say “I never killed someone and hid him/her in the sand”. Well, what is the difference with Mose’s act and insulting a fellow human being?
This could be attested by Matthew 5:22:

“but I say unto you, that every one who is angry with his brother shall be in danger of the judgment; and whosoever shall say to his brother, Raca, shall be in danger of the council; and whosoever shall say, Thou fool, shall be in danger of the hell of fire.”

Michelangelo, Moses (1514)