Wikipedia
Ex opere operato is a Latin phrase meaning "from the work worked" referring to sacraments deriving their power from Christ's work (ex opere operato Christi) rather than the role of humans. The phrase is commonly misunderstood to mean that sacraments work automatically and independently of the faith of the recipient. However, In order to receive sacraments fruitfully, it is believed necessary for the recipient to have faith. In modern usage, the phrase often refers to the idea that sacraments are efficacious in and of themselves rather than depending on the attitude either of the minister or the recipient. For example, Confirmation might be held to bestow the Holy Spirit regardless of the attitude of both the bishop and the person being confirmed.