en_tn/num/16/04.md

he lay face down

This was a posture of submission and indicates that Moses was praying to Yahweh and fearful of how he might react to the people's rebellion.

who is reserved for Yahweh

AT: "whom Yahweh has reserved for himself" (See: rc://en/ta/man/translate/figs-activepassive)

bring him up to himself

Here the word "him" refers to the man whom Yahweh chooses and "himself" refers to Yahweh.