Or HaChaim on Deuteronomy 32:38/אור החיים על דברים ל״ב:ל״ח

1 יקומו ויעזרכם, "Let them arise and help you!" There are two kinds of idolatry and idolators. 1) Someone is wholly committed to serve idols for their own sake. 2) Someone who only serves idols for self-serving purposes, i.e. in order to manipulate the deity for his own purpose. G'd forbade both kinds of idolatry in Exodus 20,4. Concerning the person who only goes through the motions of serving an idol for what he expects to get out of it, G'd said here: "let the deity arise and help you, i.e. you will be sorely disappointed." Concerning the other type of idolator G'd says sarcastically: יהי עליכם סתרה, "let them be a hide-out for you!"

2אשר חלב זבחמו יאכלו, "the fat of whose offerings they used to eat, etc." This is G'd's response to their words. The sequence of the words here has to be read as follows: "For G'd will judge His people…and He will then relent considering all they have already suffered, taking into consideration also their present state of utter helplessness plus the fact that after all the people do turn to Him." G'd then responds that those who used to offer sacrifices and eat the fat parts themselves experienced that not therein lay their salvation יקומו. They should arise (anew) in order to finally realise that their salvation did not lie in the number of their sacrifices but that only G'd is the Saviour. This is the meaning of ראו עתה כי אני השם, "See, now, that only I am the Lord" (verse 39).