Romanos 4:19-21

Even though Abraham’s faith was stronger at some times than it was at others (cf. Genesis 17:17; Genesis 17:23-27), Paul could say he was not weak in faith (Romans 4:19).

"When Paul says that Abraham did not ’doubt . . . because of unbelief,’ he means not that Abraham never had momentary hesitations, but that he avoided a deep-seated and permanent attitude of distrust and inconsistency in relationship to God and his promises." [Note: Moo, pp. 284-85. Cf. James 1:6-8.]

The patriarch believed God in the face of discouraging facts that he contemplated courageously. He believed despite the knowledge that what God had promised could not happen naturally. Abraham grew stronger in faith as time passed. The record of his life in Genesis shows this (Romans 4:20). He gave glory to God by believing Him.