This is probably a reach but here goes.
Thus Abraham "believed God, and it was reckoned to him as righteousness." 7 So you see that it is men of faith who are the sons of Abraham. (Galatians (RSV) 3)
In Hebrews:39 And all these, though well attested by their faith, did not receive what was promised, 40 since God had foreseen something better for us, that apart from us they should not be made perfect. (Hebrews (RSV) 11)
1 Therefore, since we are surrounded by so great a cloud of witnesses, let us also lay aside every weight, and sin which clings so closely, and let us run with perseverance the race that is set before us, 2 looking to Jesus the pioneer and perfecter of our faith, who for the joy that was set before him endured the cross, despising the shame, and is seated at the right hand of the throne of God. (Hebrews (RSV) 12)
So here are some thoughts and observations:
1. It is not clear if Abram worshiped 1 God who is the 1 true God. The history of the times presents the times of Abraham as "polytheistic".
2. So concluding Abram being polytheistic, it was by God's grace that Abram responded to God's "invitation."
3. God "revealed" Himself and Abram does not say that the God He was following is the 1 True God so possibly Abram although following God's call was still "polytheistic."
4. Abram was "converted" into Abraham by his obedience and trust in God thus Abram was "righteous" in the eyes of God
5. Abram is honored by St. Paul and was saved through the merits of Jesus Christ without "knowing Him."
So the life of Abraham is a scriptural witness to the validity that a person need not be a "Christian" in order to be deemed righteous" in God's eyes and be saved through the grace granted by God through our Lord and Saviour Jesus Christ.
It is also a witness to the Baptism of Desire by the Gospel passage referencing David's longing to see that day.