Cardinal Manning states that the third effect of mortal sin “is even more terrible; it mortifies and kills the very power of serving God.”
“All the actions of a man in a state of mortal sin are dead; they have no merit or power to prevail before God for his salvation. So long as he is separated from God, nothing he does has saving power.” He is like a dead tree, which “has nothing but fruit that is withered and dead likewise.”
“The Apostle has declared this, in the most express words: ‘Though I speak with the tongue of men and of angels, and have not charity, I become as sounding brass and a tinkling cymbal; and if I have all prophecy and all knowledge, and can understand all mysteries, and though I have faith and could remove mountains, and have not charity, I am nothing; and though I give my goods to feed the poor and my body to be burned, and have not charity, it profiteth me nothing’ (1 Cor 13:1-3): that is to say, a soul separated from God, not having the love of God; it matters not what that soul may know, it may be able to prophesy, to expound mysteries, to work miracles: it may give all it possesses to the poor in alms, it may be martyred, as men may think, and yet if it have not the love of God it profits nothing to salvation.”
“There will be at the last day those who will come to our Divine Lord and say, ‘Lord! Lord! we prophesied in Thy name, we cast out devils and did many mighty works in Thy name; we have eaten and drunk in Thy presence; and He will say unto them, Depart from Me, I never knew you’ (Mt 7:22-23): that is to say, a soul that has sinned unto death by one sin, one transgression, continuing in that state, until restored to union with God by charity and by grace, is dead before God, and all the actions of the soul are dead.”
Quotations from Henry Edward Manning, Sin and Its Consequences, 2d ed. (London: Burns and Oates, 1874).