en_tn_condensed/deu/31/28.md

so that I may speak these words in their ears

"so that I may speak the words of this song to them"

call heaven and earth to witness against them

Possible meanings are 1) Moses is calling on all those who live in heaven and earth to be witnesses. or 2) Moses is speaking to heaven and earth as if they are people, and he is calling them to be witnesses.