2 For even among the heretics, they who for their iniquities and errors have suffered any trouble, vaunt themselves in the name of martyrdom, that with this fair covering disguised they may plunder the more easily, for wolves they are. Now if you would know in what rank they are to be held, hear that good shepherd, the Apostle Paul, that not all who even give up their bodies in suffering to the flames, are to be accounted to have shed their blood for the sheep, but rather against the sheep.
“If,” says he, “I speak with the tongues of men, and angels, but have not charity, I have become as sounding brass, or a tinkling cymbal. If I should know all mysteries, and have all prophecy, and all faith, so that I could remove mountains, but have not charity, I am nothing.” Now a great thing truly is this faith that removes mountains. They are indeed all great things; but if I have them without charity, says he, not they, but I am nothing. But up to this point he has not touched them, who glory in sufferings under the false name of martyrdom.
Hear how he touches, yea rather pierces them through and through. “If I should distribute,” says he, “all my goods to the poor, and deliver my body to be burned.” Now here they are. But mark what follows; “but have not charity, it profits me nothing.” Lo, they have come to suffering, come even to the shedding of blood, yea come to the burning of the body; and yet it profits them nothing, because charity is lacking. Add charity, they all profit; take charity away, all the rest profit nothing.
Source: Sermons on Selected Lessons of the New Testament (New Advent)