"They are the children of God because they are the ones who will rise"
As a sacrament born from the mystery of Redemption and, in a certain sense, reborn from the nuptial love between Christ and the Church (cf. Eph 5,22-23), marriage is an efficacious expression of God's saving power, bringing to realization his eternal design even after sin and in spite of the concupiscence that is hidden in the hearts of every human being, both man and woman... As a sacrament of the Church, marriage is by nature indissoluble. As a sacrament of the Church it is also a word spoken by the Spirit, who exhorts man and woman to shape their whole life together by drawing strength from the mystery of the redemption of the body... The redemption of the body means... that hope which, in the context of marriage, can be defined as hope in daily life, hope in what is temporal...
The dignity of married couples... is expressed in their profound awareness of the sanctity of life, to which both contribute by participating – as co-founders of a family – in the forces belonging to the mystery of creation. In the light of this hope, which is linked to the mystery of the redemption of the body, this new human life, the child conceived and born of the conjugal union of its father and mother, opens itself to the «firstfruits of the Spirit» «to enter into the freedom of the glory of the children of God». And if «all creation is groaning in labor pains even until now», a special hope accompanies the woman in the pains of childbirth, namely the hope of «the revelation of the children of God» (cf. Rm 8,19-23), a hope of which every newborn child carries a spark when it comes into the world... This is what Christ's words refer to when he called attention to the resurrection of the body... «They are children of God, being children of the resurrection.