Neither Charity nor ‘Martyrdom’ Can Win Salvation for Non-Catholics
The heresy of universal salvation has never been so broadly and profoundly preached and believed as it is in our times. Therefore, it seems opportune to remind our[selves] of the text of the Bull Cantate Domino by Pope Eugene IV (February 4, 1442), confirmed by the Council of Florence. It clearly states that neither works of charity nor even the 'martyrdom' of non-Catholics is of any avail for their salvation. If they do not enter the Catholic Church, they will go to Hell.
“The Holy Roman Church firmly believes, professes and preaches that all those who are outside the Catholic Church, not only pagans but also Jews or heretics and schismatics, cannot have a share in eternal happiness; but that they will go into the everlasting fire which was prepared for the Devil and his Angels(Matt 25: 41), unless they unite themselves to the Church before their death; and that so precious is the unity of this ecclesiastical body that only those who abide in it can benefit from the Church’s Sacraments for their salvation, and that they alone can receive an eternal recompense for their fasts, almsgiving and other works of piety and practices of the Christian militancy. No one, no matter how much he has given in alms and even if he has shed blood for the name of Christ, can be saved, unless he has persevered in the bosom and the unity of the Catholic Church.”
(Pope Eugene IV, Cantate Domino, Denzinger n. 714)
"So let us be confident, let us not be unprepared, let us not be outflanked, let us be wise, vigilant, fighting against those who are trying to tear the faith out of our souls and morality out of our hearts, so that we may remain Catholics, remain united to the Blessed Virgin Mary, remain united to the Roman Catholic Church, remain faithful children of the Church."- Archbp. Lefebvre 1980