59 And inasmuch as when such things are either provided against the time to come, or reserved, if there is no cause wherefore you should expend them, it is uncertain with what intention it is done, since it may be done with a single heart, and also with a double one, He has seasonably added in this passage: “Judge not, that you be not judged. For with what judgment ye judge, you shall be judged, and with what measure ye mete, it shall be measured to you again.” In this passage, I am of opinion that we are taught nothing else, but that in the case of those actions respecting which it is doubtful with what intention they are done, we are to put the better construction on them. For when it is written, “By their fruits you shall know them,” the statement has reference to things which manifestly cannot be done with a good intention; such as debaucheries, or blasphemies, or thefts, or drunkenness, and all such things, of which we are permitted to judge, according to the apostle's statement: “For what have I to do to judge them also that are without? Do not ye judge them that are within?” But concerning the kind of food, because every kind of human food can be taken indiscriminately with a good intention and a single heart, without the vice of concupiscence, the same apostle forbids that they who ate flesh and drank wine be judged by those who abstained from such kinds of sustenance: “Let not him that eats,” says he, “despise him that eats not; and let not him which eats not, judge him that eats.” There also he says: “Who are you that judges another man's servant? To his own master he stands or falls.” For in reference to such matters as can be done with a good and single and noble intention, although they may also be done with an intention the reverse of good, those parties wished, howbeit they were [mere] men, to pronounce judgment upon the secrets of the heart, of which God alone is Judge.
60. To this category belongs also what he says in another passage: “Therefore judge nothing before the time, until the Lord come, who both will bring to light the hidden things of darkness, and will make manifest the thoughts of the hearts: and then shall every man have praise of God.” There are therefore certain ambiguous actions, respecting which we are ignorant with what intention they are performed, because they may be done both with a good or with an evil one, of which it is rash to judge, especially for the purpose of condemning. Now the time will come for these to be judged, when the Lord “will bring to light the hidden things of darkness, and will make manifest the counsels of the hearts.” In another passage also the same apostle says: “Some men's aims are manifest beforehand, going before to judgment; and some men they follow after.” He calls those sins manifest, with regard to which it is clear with what intention they are done; these go before to judgment, because if a judgment shall follow, it is not rash. But those which are concealed follow, because neither shall they remain hid in their own time. So we must understand with respect to good works also. For he adds to this effect: “Likewise also the good works of some are manifest beforehand; and they that are otherwise cannot be hid.” Let us judge, therefore, with respect to those which are manifest; but respecting those which are concealed, let us leave the judgment to God: for they also cannot be hid, whether they be good or evil, when the time shall come for them to be manifested.
61. There are two things, moreover, in which we ought to beware of rash judgment; when it is uncertain with what intention any thing is done; or when it is uncertain what sort of a person he is going to be, who at preset is manifestly either good or bad. If, therefore, any one, for example, complaining of his stomach, would not fast, and you, not believing this, were to attribute it to the vice of gluttony, you would judge rashly. Likewise, if you were to come to know the gluttony and drunkenness as being manifest, and were so to administer reproof as if the man could never be amended and changed, you would nevertheless judge rashly. Let us not therefore reprove those things about which we do not know with what intention they are done; nor let us so reprove those things which are manifest, as that we should despair of a return to a right state of mind; and thus we shall avoid the judgment of which in the present instance it is said, “Judge not, that you be not judged.”
62. But what He says may cause perplexity: “For with what judgment ye judge, you shall be judged; and with what measure ye mete, it shall be measured to you again.” Is it the case, then, that if we shall judge any thing with a rash judgment, God will also judge rashly with respect to us? Or if we shall measure any thing with an unjust measure, is there with God also an unjust measure, according to which it shall be measured to us again? (for by the expression measure also, I suppose the judgment itself is meant.) By no means does God either judge rashly, or recompense to any one with an unjust measure; but it is so expressed, inasmuch as that very same rashness wherewith you punish another must necessarily punish yourself. Unless, perchance, it is to be imagined that injustice does harm in some way to him against whom it goes forth, but in no way to him from whom it goes forth; but nay, it often does no harm to him who suffers the injury, but it must necessarily do harm to him who inflicts it. For what harm did the injustice of the persecutors do to the martyrs? None; but very much to the persecutors themselves. For although some of them were turned from the error of their ways, yet at the time at which they were acting as persecutors, their wickedness was blinding them. So also a rash judgment frequently does no harm to him who is the object of the rash judgment; but to him who judges rashly, the rashness itself must necessarily do harm. According to such a rule, I judge of that saying also: “Every one that strikes with the sword shall perish with the sword.” For how many take the sword, and yet do not perish with the sword, Peter himself being an instance! But lest any should think that he escaped such punishment by the pardon of his sins (although nothing could be more absurd than to think that the punishment of the sword, which did not befall Peter, could have been greater than that of the cross, which actually befell him), yet what would they say of the malefactors who were crucified with our Lord; for both he who got pardon, got it after he was crucified, and the other did not get it at all? Or had they perhaps crucified all whom they had slain; and did they therefore themselves too deserve to suffer the same thing? It is ridiculous to think so. For what else is meant by the statement, “For all they that take the sword shall perish with the sword,” but that the soul dies by that very sin, whatever it may be, which it has committed?
Source: Our Lord's Sermon on the Mount (New Advent)