Deuteronomy 31:2-6

And he said to them: “I am one hundred and twenty years old today. I can no longer go out and come in. Also the LORD has said to me, ‘You shall not cross over this Jordan.’ The LORD your God Himself crosses over before you; He will destroy these nations from before you, and you shall dispossess them. Joshua himself crosses over before you, just as the LORD has said. And the LORD will do to them as He did to Sihon and Og, the kings of the Amorites and their land, when He destroyed them. The LORD will give them over to you, that you may do to them according to every commandment which I have commanded you. Be strong and of good courage, do not fear nor be afraid of them; for the LORD your God, He is the One who goes with you. He will not leave you nor forsake you.”