The Gospel, English, p. 14
GRACE: A FREE GIFT
The word “grace” means something which is given freely . . . without cost or obligation. For example, if your best friend offered you a gift and you tried to pay him for it, could you still call it a gift? Of course not. It becomes a debt which he owes you the moment he accepts your money! Your friend would probably be insulted, withdraw the gift and say: “I’m not giving this to you because I have to. It is a gift. Do you accept my gift or not?”
A GIFT: THE MOMENT YOU OFFER SOMETHING IN EXCHANGE FOR IT, IT IS NO LONGER A GIFT. IT BECOMES A DEBT!
Now to him who works, his wages are not counted as grace, but as a debt. Romans 4:4
Only when you had put your money back in your pocket and stretched forth your empty hand would he renew his offer and extend the gift to you.
The same is true with God’s offer of eternal life. People try to purchase eternal life by obeying the Ten Commandments, living a good life, going to church, or some other religious work. But God will not make Himself a debtor to any man! He does not “owe” eternal life to anyone. He will offer it only as a gift!