he said to them, “I am now a hundred and twenty years old; I am no longer able to come and go, and the LORD has said to me, ‘You shall not cross the Jordan.’
He says he is now one hundred and twenty years old, can no longer lead as before, and has been told by the LORD that he will not cross the Jordan.
It states plainly why Moses' leadership is ending at the river.
1When Moses had finished speaking these words to all Israel, 2he said to them, “I am now a hundred and twenty years old; I am no longer able to come and go, and the LORD has said to me, ‘You shall not cross the Jordan.’ 3The LORD your God Himself will cross over ahead of you. He will destroy these nations before you, and you will dispossess them. Joshua will cross ahead of you, as the LORD has said. 4And the LORD will do to them as He did to Sihon and Og, the kings of the Amorites, when He destroyed them along with their land. 5The LORD will deliver them over to you, and you must do to them exactly as I have commanded you. 6Be strong and courageous; do not be afraid or terrified of them, for it is the LORD your God who goes with you; He will never leave you nor forsake you.” 7Then Moses called for Joshua and said to him in the presence of all Israel, “Be strong and courageous, for you will go with this people into the land that the LORD swore to their fathers to give them, and you shall give it to them as an inheritance. 8The LORD Himself goes before you; He will be with you. He will never leave you nor forsake you. Do not be afraid or discouraged.”