CCC 1128 This is the meaning of the Church’s affirmation¹ that the sacraments act ex opere operato (literally: “by the very fact of the action’s being performed”), i.e., by virtue of the saving work of Christ, accomplished once for all. It follows that “the sacrament is not wrought by the righteousness of either the celebrant or the recipient, but by the power of God.”² From the moment that a sacrament is celebrated in accordance with the intention of the Church, the power of Christ and his Spirit acts in and through it, independently of the personal holiness of the minister. Nevertheless, the fruits of the sacraments also depend on the disposition of the one who receives them.

1 Cf. Council of Trent (1547): DS 1608.
2 St. Thomas Aquinas, STh III, 68, 8.