John Chrysostom, on Heb 12:15

“Looking diligently, lest any man be wanting to the grace of God; lest any root of bitterness springing up do hinder, and by it many be defiled.”

“"Looking diligently lest any man fail of the grace of God." As if they were traveling together on some long journey, in a large company, he says, Take heed that no man be left behind: I do not seek this only, that ye should arrive yourselves, but also that ye should look diligently after the others. "Lest any man" (he says) "fail of the grace of God." (He means the good things to come, the faith of the gospel, the best course of life: for they all are of "the Grace of God.") Do not tell me, It is [but] one that perisheth. Even for one Christ died. Hast thou no care for him "for whom Christ died"? "Looking diligently," he saith, that is, searching carefully, considering, thoroughly ascertaining, as is done in the case of sick persons, and in all ways examining, thoroughly ascertaining. "Lest any root of bitterness springing up trouble you." This is found in Deuteronomy; and he derived it from the metaphor of plants. "Lest any root of bitterness," he says; which he said also in another place when he writes, "A little leaven leaveneth the whole lump." Not for his sake alone do I wish this, he means, but also on account of the harm arising therefrom. That is to say, even if there be a root of this kind, do not suffer any shoot to come up, but let it be cut off, that it may not bear its proper fruits, that so it may not defile and pollute the others also. For, he saith, "Lest any root of bitterness springing up trouble you; and by it many be defiled." And with good reason did he call sin "bitter": for truly nothing is more bitter than sin, and they know it, who after they have committed it pine away under their conscience, who endure much bitterness. For being exceedingly bitter, it perverts the reasoning faculty itself. Such is the nature of what is bitter: it is unprofitable. And well said he, "root of bitterness." He said not, "bitter," but "of bitterness." For it is possible that a bitter root might bear sweet fruits; but it is not possible that a root and fountain and foundation of bitterness, should ever bear sweet fruit; for all is bitter, it has nothing sweet, all are bitter, all unpleasant, all full of hatred and abomination. "And by this" (he says) "many be defiled." That is, Cut off the lascivious persons.”

Imported from an open dataset — not yet checked against the printed edition.