en_tn_condensed/act/15/08.md

who knows the heart

Here "heart" refers to the "minds" or "inner beings." Alternate translation: "who knows the people's minds" or "who knows what people think" (See: rc://en/ta/man/translate/figs-metonymy)

witnesses to them

"witnesses to the Gentiles"

giving them the Holy Spirit

"causing the Holy Spirit to come upon them"