John Gill Commentary Joshua 1:6

"Be strong and of good courage; for thou shalt cause this people to inherit the land which I sware unto their fathers to give them." — Joshua 1:6 (ASV)

Be strong, and of good courage
The same exhortation Moses gave him, (Deuteronomy 31:7); and is afterwards repeated in this chapter, as being of great moment and importance, as it is in the general of an army to show greatness and strength of mind, valour and courage, and not be dismayed at the number and strength of the enemy. As Joshua's work in fighting with the Canaanites, and conquering their land, so Christ's work in the redemption of his people, and subduing their enemies, required strength and courage, and both were very eminent in him:

for to this people you shall divide for an inheritance the land
which I swore to their fathers to give them ;
and, this promise included and ensured the conquest of it, and the putting the people into the possession of it; for if he was to divide it to them, he must first take it out of the hands of the present inhabitants, and deliver it into the hands of the children of Israel, to be possessed by them, dividing to each tribe and family their part and portion.