Exodus 2:11-13

11And it came to pass in those days, when Moses was grown, that he went out to his brethren and looked on their burdens; and he saw an Egyptian smiting a Hebrew, one of his brethren.

12And he turned this way and that way, and when he saw that there was no man, he smote the Egyptian, and hid him in the sand.

13And he went out on the second day, and behold, two Hebrew men were quarrelling; and he said to him that was in the wrong, Why art thou smiting thy neighbour?