Numbers 35:10-15

10“Speak to the Israelites and say to them: ‘When you cross the Jordan into Canaan, 11select some towns to be your cities of refuge, to which a person who has killed someone accidentally may flee. 12They will be places of refuge from the avenger, so that anyone accused of murder may not die before they stand trial before the assembly. 13These six towns you give will be your cities of refuge. 14Give three on this side of the Jordan and three in Canaan as cities of refuge. 15These six towns will be a place of refuge for Israelites and for foreigners residing among them, so that anyone who has killed another accidentally can flee there.