Whereas previously Moses had presented Joshua to the people (vv. 1-8) now God officially commissioned him to his new responsibility as Moses' successor. He did this at the tabernacle, the appropriate place for this official ceremony.
The bulk of this section concerns God's revelation to Moses concerning Israel's future apostasy (vv. 16-22). Hiding the Lord's face (vv. 17-18; 32:20) is the opposite of making His face shine on His people and turning His face toward them in blessing (cf. Num. 6:25-26). To discourage this departure God gave Moses a song that he was to write down and teach the people to remind them of God's faithfulness. As a song the people would have repeated these words frequently and remembered them easily. The singing of it would haunt them with how much they had lost for disobeying Yahweh.
