he - Jehovah “said,” that is, thought, in choosing them as His covenant-people; so “said” (Psa 95:10). Not that God was ignorant that the Jews would not keep faith with Him; but God is here said, according to human modes of thought to say within Himself what He might naturally have expected, as the result of His goodness to the Jews; thus the enormity of their unnatural perversity is the more vividly set forth.
lie - prove false to Me (compare Psa 44:17).
so - in virtue of His having chosen them, He became their Savior. So the “therefore” (Jer 31:33). His eternal choice is the ground of His actually saving men (Eph 1:3, Eph 1:4).