St. Robert Bellarmine, De Controversiis, “De Baptismo,” Lib. I, Cap. VI: “But without doubt it must be believed that true conversion supplies for Baptism of water when one dies without Baptism of water not out of contempt but out of necessity... For it is expressly said in Ezechiel: If the wicked shall do penance from his sins, I will no more remember his iniquities...Thus also the Council of Trent, Session 6, Chapter 4, says that Baptism is necessary in fact or in desire (in re vel in voto)”.
Our Lord Jesus Christ, Prince of Theologians, to St. Catherine of Sienna: I wished thee to see the secret of the Heart, showing it to thee open, so that you mightest see how much more I loved than I could show thee by finite pain. I poured from it Blood and Water, to show thee the baptism of water which is received in virtue of the Blood. I also showed the baptism of love in two ways, first in those who are baptized in their blood shed for Me which has virtue through My Blood, even if they have not been able to have Holy Baptism, and also those who are baptized in fire, not being able to have Holy Baptism, but desiring it with the affection of love. There is no baptism of desire without the Blood, because Blood is steeped in and kneaded with the fire of Divine charity, because through love was it shed.
There is yet another way by which the soul receives the baptism of Blood, speaking, as it were, under a figure, and this way the Divine charity provided, knowing the infirmity and fragility of an, through which he offends, not that he is obliged, through his fragility and infirmity, to commit sin, unless he wish to do so; by falling, as he will, into the guild of mortal sin, by which he loses the grace which he drew from Holy Baptism in virtue of the Blood, it was necessary to leave a continual baptism of blood.
This the Divine charity provided in the Sacrament of Holy Confession, the soul receiving the Baptism of blood, with contrition of heart, confessing, when able, to My ministers, who hold the keys of the Blood, sprinkling It, in absolution, upon the face of the soul. But if the soul is unable to confess, contrition of heart is sufficient for this baptism, the hand of My clemency giving you the fruit of this precious Blood... Thou seest then that these Baptisms, which you should all receive until the last moment, are continual, and though My works, that is the pains of the Cross were finite, the fruit of them which you receive in Baptism, through Me, are infinite..."