Deuteronomy 4:41

39Know therefore today, and take it to heart, that the LORD himself is God in heaven above and on the earth beneath. There is no one else.

40You shall keep his statutes and his commandments which I command you today, that it may go well with you and with your children after you, and that you may prolong your days in the land which the LORD your God gives you for all time.

41Then Moses set apart three cities beyond the Jordan toward the sunrise,

42that the man slayer might flee there, who kills his neighbor unintentionally and didn’t hate him in time past, and that fleeing to one of these cities he might live:

43Bezer in the wilderness, in the plain country, for the Reubenites; and Ramoth in Gilead for the Gadites; and Golan in Bashan for the Manassites.