Tertullian, Church Father (3rd Century): On Baptism, Chapter XVI, Of the Second Baptism - With Blood: "We have indeed, likewise, a second font, (itself withal one with the former,) of blood, to wit; concerning which the Lord said, "I have to be baptized with a baptism,"when He had been baptized already. For He had come "by means of water and blood,"just as John has written; that He might be baptized by the water, glorified by the blood; to make us, in like manner, called by water, chosen by blood. These two baptisms He sent out from the wound in His pierced side, in order that they who believed in His blood might be bathed with the water; they who had been bathed in the water might likewise drink the blood. This is the baptism which both stands in lieu of the fontal bathing when that has not been received, and restores it when lost."
Scorpiace: Antidote for the Scorpion's Sting, Ch VI: "He therefore appointed as second supplies of comfort, and the last means of succour, the fight of martyrdom and the baptism--thereafter free from danger--of blood. And concerning the happiness of the man who has partaken of these, David says: "Blessed are they whose iniquities are forgiven, and whose sins are covered. Blessed is the man to whom the Lord will not impute sin." For, strictly speaking, there cannot any longer be reckoned ought against the martyrs, by whom in the baptism (of blood) life itself is laid down. Thus, "love covers the multitude of sins;" and loving God, to wit, with all its strength (by which in the endurance of martyrdom it maintains the fight), with all its life (which it lays down for God), it makes of man a martyr."