Why does the word redemption have to be used of God's saving work?
Redemption must be used because God’s saving work involves buying back what He once owned and lost. Scripture says all sinned, so God justifies freely by grace through redemption. You do not buy something back unless you previously owned it and lost it; Satan took control, and God must pay the price to reclaim it.
Les explains that the first thing to qualify is why the word redemption has to be used: you do not buy something back unless you have owned it and lost it. He illustrates this with a hock shop—if you hock an item, you took a loan against it, and the holder controls it until you pay the redemption price. So it is in Scripture: God had to pay a price of redemption, first for Israel nationally and for the whole world in general, because that which was once God’s was lost. Satan picked it up and holds it tight until God pays the price of redemption. Israel’s loss goes back to when Joseph’s brothers sold him into slavery; it was sinful and wrong, and God lost control of the embryonic nation. They ended up in Egypt under the Egyptian yoke for 215 years, until they came out as recorded in Exodus.