C. F. Keil and Franz Delitzsch on Deuteronomy 4:20

Deu 4:20

The Israelites were not to imitate the heathen in this respect, because Jehovah, who brought them out of the iron furnace of Egypt, had taken them (לקח) to Himself, i.e., had drawn them out or separated them from the rest of the nations, to be a people of inheritance. They were therefore not to seek God and pray to Him in any kind of creature, but to worship Him without image and form, in a manner corresponding to His own nature, which had been manifested in no form, and therefore could not be imitated. בּרזל כּוּר, an iron furnace, or furnace for smelting iron, is a significant figure descriptive of the terrible sufferings endured by Israel in Egypt. נחלה עם (a people of inheritance) is synonymous with סגלּה עם (a special people, Deu 7:6 : see at Exo 19:5, “a peculiar treasure”). “This day:” as in Deu 2:30.