obey his voice

Here "voice" is referring to what Yahweh says. Alternate translation: "obey what he says" (See: rc://en/ta/man/jit/figs-metonymy)

with all your heart and with all your soul

Here "heart" and "soul" are metonyms for a person's inner being. These two phrases are used together to mean "completely" or "earnestly." See how you translated these words in Deuteronomy 4:29. (See: rc://en/ta/man/jit/figs-metonymy and rc://en/ta/man/jit/figs-doublet)