"Now, Lord, I am not taking this kinswoman of mine because of lust, but with sincerity." (Tobit 8:7)
Before they sleep together, Tobias does as Raphael instructed: he takes the fish's heart and liver and puts them on the charcoal incense burner. The smell drives the demon Asmodeus away to Upper Egypt, where Raphael binds him. Raguel's servants dig a grave, expecting Tobias to be dead by morning. Tobias and Sarah pray together: blessed are you, God of our ancestors; blessed be your name forever. You made Adam, and Eve his wife to help him and support him. Then the prayer of Tobias: Now, Lord, I am not taking this kinswoman of mine because of lust, but with sincerity. Grant that she and I may find mercy and that we may grow old together. He sleeps. In the morning the servants find them alive.
The Catechism cites the prayer of Tobias and Sarah on their wedding night as one of the foundational texts for the theology of Christian marriage: the marriage entered in prayer, with sincerity rather than lust, is placed under divine protection (CCC 1611).
Brothers and sisters, I am not taking her because of lust, but with sincerity. The distinction between the desire that reduces the other to an object and the love that approaches in sincerity is the distinction between the lustful and the covenantal. Every marriage needs Tobias's prayer: not for lust but for sincerity, not for gratification but for mercy, not for the night but for growing old together.
Lord God, we approach every covenant relationship not for lust but with sincerity. Grant us mercy and let us grow old together. Through Christ our Lord. Amen.