This practice of Abraham must also become ours. If we come to doubt or begin to despair, if we feel no comfort, then we must call to mind Abraham's practice. He believed God's promise, even when the visible foundation of that promise was unknown and unsure. When the promises of God seem to be far from us and their accomplishment to be impossible, then we must cast our souls upon these very promises. When we feel we are in the very grip of hell, then, then especially, we must believe God's promises.
Faith is a persuasion and assent to truth upon the authority of another.
We must both believe and practice. By this we believe ourselves utterly sinful, lost, and undone, without Jesus Christ. So we trust and depend on His righteousness as the ground of salvation to us in particular. By saving faith we are united to His person, as our spiritual head and husband and are given His righteousness. It works by love for the performance of every good word and work, Gal.