Abraham is to us the great exemplar of faith, and also of the assurance of faith. He was fully assured that what God had promised He was able also to perform. His expectation was only from God, and what God had promised. This is wrong. As I have need of nothing more than the word of a trustworthy man to give me complete certitude, so must the word of God be my certitude.
People err because they seek something in themselves and in their feeling.
He does not doubt the promises, but is strong in faith, giving God the glory, and being fully assured that what was promised God is also able to perform. The godless man who receives grace knows this only from the word. But then, later on, assurance is to follow from works. But when the time of fruit arrives, and no fruit appears, then I may doubt. The more clearly I at the outset hold the assurance of faith, without works, on the word alone, the more certainly shall works follow.