11 A final element of the story of Abraham is important for understanding his faith. God’s word, while bringing newness and surprise, is not at all alien to Abraham’s experience. In the voice which speaks to him, the patriarch recognizes a profound call which was always present at the core of his being. God ties his promise to that aspect of human life which has always appeared most "full of promise", namely, parenthood, the begetting of new life: "Sarah your wife shall bear you a son, and you shall name him Isaac" ( Gen 17:19). The God who asks Abraham for complete trust reveals himself to be the source of all life. Faith is thus linked to God’s fatherhood, which gives rise to all creation; the God who calls Abraham is the Creator, the one who "calls into existence the things that do not exist" ( Rom 4:17), the one who "chose us before the foundation of the world… and destined us for adoption as his children" ( Eph 1:4-5). For Abraham, faith in God sheds light on the depths of his being, it enables him to acknowledge the wellspring of goodness at the origin of all things and to realize that his life is not the product of non-being or chance, but the fruit of a personal call and a personal love. The mysterious God who called him is no alien deity, but the God who is the origin and mainstay of all that is. The great test of Abraham’s faith, the sacrifice of his son Isaac, would show the extent to which this primordial love is capable of ensuring life even beyond death. The word which could raise up a son to one who was "as good as dead", in "the barrenness" of Sarah’s womb (cf. Rom 4:19), can also stand by his promise of a future beyond all threat or danger (cf. Heb 11:19; Rom 4:21).
Source: Lumen Fidei (Vatican.va)