Numbers 35:20-23

20Likewise, if anyone maliciously pushes another or intentionally throws an object at him and kills him, 21or if in hostility he strikes him with his hand and he dies, the one who struck him must surely be put to death; he is a murderer. When the avenger of blood finds the murderer, he is to kill him.

22But if anyone pushes a person suddenly, without hostility, or throws an object at him unintentionally, 23or without looking drops a heavy stone that kills him, but he was not an enemy and did not intend to harm him,