Faith assures us of things we expect and convinces us of the existence of things we cannot see. God accepted our ancestors because of their faith.
Faith convinces us that God created the world through his word. This means what can be seen was made by something that could not be seen.
Faith led Abel to offer God a better sacrifice than Cain’s sacrifice. Through his faith Abel received God’s approval, since God accepted his sacrifices. Through his faith Abel still speaks, even though he is dead. Hebrews 11: 1-4