Deuteronomy 3:21

“And I commanded Joshua at that time, etc.] After the conquest of the two kings, and the assignment of their countries to the above tribes; and after Moses had it made known to him that he should quickly die, and Joshua should be his successor; then, by the direction of God, he gave him the following charge: saying, thine eyes have seen all that the Lord your God hath done unto these two kings; Sihon and Og; how their kingdoms were taken from them, and given to Israel, and they slain with the sword; this Joshua was an eyewitness of, and was, no doubt, greatly concerned in the battles with them, being the general in the Israelitish armies; at least this was sometimes his post, and he cannot be…”

“3:21-29 See Num 20:2-13; Ps 106:32-33. 3:21 He will do the same: Israel’s military success under Moses’ leadership could be expected to continue under Joshua because the Lord promised to remain with them.”

“I commanded: Num 27:18-23 so shall: Jos 10:25; Sa1 17:36, Sa1 17:37; Psa 9:10; Co2 1:10, Co2 12:10; Eph 3:20; Ti2 4:17, Ti2 4:18 Deuteronomy 3:22”

“Nomination of Joshua as his Successor. - This reminiscence also recalls the goodness of God in the appointment of Joshua ( Num 27:12.), which took place "at that time," i.e., after the conquest of the land on the east of the Jordan. In accordance with the object of his address, which was to hold up to view what the Lord had done for Israel, he here relates how, at the very outset, he pointed Joshua to the things which he had seen with his eyes (הראת עיניך, thine eyes were seeing; cf. Ewald, 335, b.), namely, to the defeat of the two kings of the Amorites, in which the pledge was contained, that the faithful covenant God would complete the work He had begun, and would do the same to all…”