32 Nor must it be forgotten that personal unworthiness does not hinder the efficacy of a priest's ministry. For the unworthiness of the minister does not make void the Sacraments he administers; since the Sacraments derive their efficacy from the Blood of Christ, independently of the sanctity of the instrument, or, as scholastic language expresses it, the Sacraments work their effect ex opere operato .
Source: Ad Catholici Sacerdotii (Vatican.va)