Numbers 35:14
Three on the other side of Jordan and three in the land of Canaan, to be safe places for flight.
Deuteronomy 4:41-43
Then Moses had three towns marked out on the far side of Jordan looking to the east;
Deuteronomy 19:8-10
And if the Lord your God makes wide the limits of your land, as he said in his oath to your fathers, and gives you all the land which he undertook to give to your fathers;
Joshua 20:7-9
So they made selection of Kedesh in Galilee in the hill-country of Naphtali, and Shechem in the hill-country of Ephraim, and Kiriath-arba (which is Hebron) in the hill-country of Judah.