John Gill Commentary Joshua 1:13

"Remember the word which Moses the servant of Jehovah commanded you, saying, Jehovah your God giveth you rest, and will give you this land." — Joshua 1:13 (ASV)

Remember the word which Moses the servant of the Lord
commanded you
In (Numbers 32:29Numbers 32:30) ; and to which they had solemnly agreed; and, now the time was come to put it into execution, Joshua reminds them of it:

saying, the Lord your God has given you rest :
from their travels, and a settlement in a country agreeably to their own desire:

and has given you this land ;
where they now were, and which they had taken from Sihon and Og, kings of the Amorites, and joined to Moab, on the borders of which Israel lay encamped; and by this it appears, that the settlement of these tribes, on the other side Jordan, was according to the will of God; he gave it to them.