Or HaChaim on Deuteronomy 32:18/אור החיים על דברים ל״ב:י״ח

1 צור ילדך תשי, "You neglected the Rock that begot you;" This is best understood in connection with Sanhedrin 38 that at the time G'd was about to create man, He consulted with the angels about His project. Some angels strenuously opposed the creation of man. G'd not only ignored these angels and created man, but He punished the angels who had opposed man's creation. Whenever Israel sins this weakens G'd's argument in favour of having created man. This is what Moses meant when he said ילדך תשי, "you weaken the One who begot you."

2ותשכח אל מחללך, "You forgot the G'd who brought you forth." The word מחללך may be understood as a reference to jewels as in Hoseah 2,15 ותעד נזמה וחליתה, "when she was decked out with her nose-rings and her jewelry," etc. What Moses means is that Israel forgot the very G'd who had made her a more precious jewel than any other creature including the angels. Compare Psalms 66,12, or Isaiah 49,3 "Israel in whom I glory." G'd means that He wears the name of Israel like a person wears a jewel. Our sages have offered a variety of interpretations of this verse.