21 But this impenitence or impenitent heart may not be pronounced upon, as long as a man lives in the flesh. For we are not to despair of any so long as “the patience of God leads the ungodly to repentance,” and does not hurry him out of this life; “God, who wills not the death of a sinner, but that he should return from his ways and live.” He is a heathen today; but how do you know whether he may not be a Christian tomorrow? He is a heretic today; but what if tomorrow he follow the Catholic truth?
He is a schismatic today; but what if tomorrow he embrace Catholic peace? What if they, whom you observe now in any kind of error that can be, and whom you condemn as in most desperate case, what if before they end this life, they repent and find the true life in that which is to come? Wherefore, Brethren, let also what the Apostle says urge you to this. “Judge nothing before the time.” For this blasphemy of the Spirit, for which there is no forgiveness (which I have understood to be not every kind of blasphemy, but a particular sort, and that as I have said or discovered, or even as I think clearly shown to be the case, the persevering hardness of an impenitent heart), cannot be taken hold of in any one, I repeat it, as long as he is still in this life.
Source: Sermons on Selected Lessons of the New Testament (New Advent)