For those who placed their trust in Christ, God’s grace is the environment in which they live and move and have their being. And faith is the basic posture of living in God’s grace. Why? Because God’s grace, as it is God’s free gift to sinners, is not something we can pay or work for; it is something we gratefully receive by faith as a gift. We need faith to receive it 1) because it is a spiritual gift, which we cannot see with our eyes and receive with our hands: we receive it by trusting God’s promise-keeping character; 2) because it is too good to be true in its enormous value, benefit, and impact.
Faith, then, has two effects on us. First, it humbles us because it recognizes God's grace as the efficient cause of our salvation as well as all the blessings we enjoy in this life and the life to come. There is nothing we can contribute to our salvation. Whatever good work we do as believers doesn’t count toward our salvation since it is not so much something we do for our salvation as it is something we do as a result of our salvation. It’s like a child being adopted. Whatever good he does is not so he can be adopted—he is already adopted by grace, as it were; it is because he is now part of the family, for which he is grateful. The faith which recognizes God’s pervasive grace in our salvation is a humble faith.