Romans 4:14

To introduce law-keeping as a condition for the fulfillment of this promise would have two effects. First, it would make faith irrelevant. It would subject this simple unconditional promise to the condition of human obedience. If, for example, a father promised his son a new bicycle, the boy would look forward to receiving it as a gift. However if the father added the condition that to get the bike the boy had to be obedient, he would destroy his son’s confidence that he would get the bike. Now obtaining the bicycle depended on obedience. It was no longer a matter of faith. The second effect, which is also evident in this illustration, is that the promise would be nullified (i.e., made worthless).