52 In Abraham’s journey towards the future city, the Letter to the Hebrews mentions the blessing which was passed on from fathers to sons (cf. Heb 11:20-21). The first setting in which faith enlightens the human city is the family. I think first and foremost of the stable union of man and woman in marriage. This union is born of their love, as a sign and presence of God’s own love, and of the acknowledgment and acceptance of the goodness of sexual differentiation, whereby spouses can become one flesh (cf. Gen 2:24) and are enabled to give birth to a new life, a manifestation of the Creator’s goodness, wisdom and loving plan. Grounded in this love, a man and a woman can promise each other mutual love in a gesture which engages their entire lives and mirrors many features of faith. Promising love for ever is possible when we perceive a plan bigger than our own ideas and undertakings, a plan which sustains us and enables us to surrender our future entirely to the one we love. Faith also helps us to grasp in all its depth and richness the begetting of children, as a sign of the love of the Creator who entrusts us with the mystery of a new person. So it was that Sarah, by faith, became a mother, for she trusted in God’s fidelity to his promise (cf. Heb 11:11).
Source: Lumen Fidei (Vatican.va)