Well, I'm not sure how it worked with Abram. As you say, he was called by God and God tested him with Isaac (and in many other ways).
But as said, I'm just not sure how redemption works for the elders (since Jesus had not yet been to the Cross).
I was hoping you could tell me.;-)
The best I can do is point you to Hebrews 11 and say it is by faith, which is a gift of God (Ephesians 2:8-10):
Verse 6 to 8:
And without faith it is impossible to please Him, for he who comes to God must believe that He is and that He is a rewarder of those who seek Him.
By faith Noah, being warned by God about things not yet seen, fnin reverence prepared an ark for the salvation of his household, by which he condemned the world, and became an heir of the righteousness which is according to faith.
By faith Abraham, when he was called, obeyed by going out to a place which he was to receive for an inheritance; and he went out, not knowing where he was going.