Numbers 35:20-23

20And if he pushed him out of hatred or hurled something at him, lying in wait, so that he died,

21or in enmity struck him down with his hand, so that he died, then he who struck the blow shall be put to death. He is a murderer. The avenger of blood shall put the murderer to death when he meets him.

22"But if he pushed him suddenly without enmity, or hurled anything on him without lying in wait

23or used a stone that could cause death, and without seeing him dropped it on him, so that he died, though he was not his enemy and did not seek his harm,