It was not through the lawthat the promise was made to Abraham and his descendantsthat he would inherit the world,but through the righteousness that comes from faith.For this reason, it depends on faith,so that it may be a gift,and the promise may be guaranteed to all his descendants. Romans
How hard it is for me to escape the necessary childhood formation that being obedient is the guding principle of one's life. It is no doubt necessary for children to be obedent because it keeps them safe and provides them with a stable and secure environment. But it is not a healthy principle ffor a mature person. Paul is making that point by reminding us that it is our faith in the Christ that gives us life and wholeness.
A mature Christian relies on faith, not adherence to the law. This is what explains the doubt, ambiguities and vitality of faith as opposed to a dry and lifeless obedience to a law or set of rules.