When the situation isn't what we expected, Christ encourages is to believe and fear not.

The motivation, means, encouragement and confidence of prayer.

Aaron fashions a golden calf while Moses is on Mount Sinai, and Israel worships it.  Mankind still has the tendency to fashion a god in the mind and worship it as we see fit.

Those that believe to the saving of the soul cannot draw back into perdition, because Faith coupled with God's grace keeps them. The writer shows what true Faith looks like in the lives of the OT patriarchs.

True saving faith changes those who receive it: causing them to serve God and persevere to the end.