But the LORD hath taken you, and brought you forth out of the iron furnace, even out of Egypt, to be unto him a people of inheritance, as ye are this day. Out of the iron furnace - From this mention of the word iron furnace there can be little doubt that the Israelites were employed in Egypt in the most laborious works of metallurgy. Digging, smelting, and forging of iron in so hot a climate must have been oppressive work indeed.
Related Commentaries of Deuteronomy 4:20
Deuteronomy 4:20
20 But the LORD hath taken you, and brought you forth out of the iron furnace, even out of Egypt, to be unto him a people of inheritance, as ye are this day.