But charge Joshua, and encourage him, and strengthen him: for he shall go over before this people, and he shall cause them to inherit the land which thou shalt see.

Wesley's Notes

3:28 He shall go over - It was not Moses, but Joshua or Jesus that was to give the people rest, Heb 4:8. 'Tis a comfort to those who love mankind, when they are dying and going off, to see God's work likely to be carried on by other hands, when they are silent in the dust.

Matthew Henry's Concise Commentary

3:21-29 Moses encouraged Joshua, who was to succeed him. Thus the aged and experienced in the service of God, should do all they can to strengthen the hands of those who are young, and setting out in religion. Consider what God has done, what God has promised. If God be for us, who can be against us, so as to prevail? We reproach our Leader if we follow him trembling. Moses prayed, that, if it were God's will, he might go before Israel, over Jordan into Canaan. We should never allow any desires in our hearts, which we cannot in faith offer up to God by prayer. God's answer to this prayer had a mixture of mercy and judgment. God sees it good to deny many things we desire. He may accept our prayers, yet not grant us the very things we pray for. It God does not by his providence give us what we desire, yet if by his grace he makes us content without, it comes to much the same. Let it suffice thee to have God for thy Father, and heaven for thy portion, though thou hast not every thing thou wouldst have in the world. God promised Moses a sight of Canaan from the top of Pisgah. Though he should not have the possession of it, he should have the prospect of it. Even great believers, in this present state, see heaven but at a distance. God provided him a successor. It is a comfort to the friends of the church of Christ, to see God's work likely to be carried on by others, when they are silent in the dust. And if we have the earnest and prospect of heaven, let these suffice us; let us submit to the Lord's will, and speak no more to Him of matters which he sees good to refuse us.