I find then, etc. Here Paul supposes a fourfold law. The first is the law of God, which alone is properly so called, which is the rule of righteousness, by which our life is rightly formed. To this he joins the law of the mind, and by this he means the prompt readiness of the faithful mind to render obedience to the divine law, it being a certain conformity on our part with the law of God. On the other hand, he sets in opposition to this the law of unrighteousness; and according to a certain kind of similarity, he gives this name to that dominion which iniquity exercises over a man not yet regenerated, as well as over the flesh of a regenerated man; for the laws even of tyrants, however iniquitous they may be, are called laws, though not properly. To correspond with this law of sin he makes the law of the members, that is, the lust which is in the members, on account of the concord it has with iniquity. As to the first clause, many interpreters take the word law in its proper sense, and consider kata or dia to be understood; and so Erasmus renders it, "by the law;" as though Paul had said, that he, by the law of God as his teacher and guide, had found out that his sin was innate. But without supplying anything, the sentence would run better thus, "While the faithful strive after what is good, they find in themselves a certain law which exercises a tyrannical power; for a vicious propensity, adverse to and resisting the law of God, is implanted in their very marrow and bones."

I find then a law - There is a law whose operation I experience whenever I attempt to do good. There have been various opinions about the meaning of the word "law" in this place. It is evident that it is used here in a sense somewhat unusual. But it retains the notion which commonly attaches to it of what binds, or controls. And though this to which he refers differs from a law, inasmuch as it is not imposed by a superior, which is the usual idea of a law, yet it has so far the sense of law that it binds, controls, influences, or is that to which he was subject. There can be no doubt that he refers here to his carnal and corrupt nature; to the evil propensities and dispositions which were leading him astray. His representing this as a law is in accordance with all that he says of it, that it is servitude, that he is in bondage to it, and that it impedes his efforts to be holy and pure. The meaning is this, "I find a habit, a propensity, an influence of corrupt passions and desires, which, when I would do right, impedes my progress, and prevents my accomplishing what I would." Compare Galatians 5:17. Every Christian is as much acquainted with this as was the apostle Paul.
Do good - Do right. Be perfect.
Evil - Some corrupt desire, or improper feeling, or evil propensity.
Is present with me - Is near; is at hand. It starts up unbidden, and undesired. It is in the path, and never leaves us, but is always ready to impede our going, and to turn us from our good designs; compare Psalm 65:3, "Iniquities prevail against me.' The sense is, that to do evil is agreeable to our strong natural inclinations and passions.

I find then a law - I am in such a condition and state of soul, under the power of such habits and sinful propensities, that when I would do good - when my will and reason are strongly bent on obedience to the law of God and opposition to the principle of sin, evil is present with me, κακον παρακειται, evil is at hand, it lies constantly before me. That, as the will to do good is constantly at hand, Romans 7:18, so the principle of rebellion exciting me to sin is equally present; but, as the one is only will, wish, and desire, without power to do what is willed, to obtain what is wished, or to perform what is desired, sin continually prevails.
The word νομος, law, in this verse, must be taken as implying any strong or confirmed habit, συνηθεια, as Hesychius renders it, under the influence of which the man generally acts; and in this sense the apostle most evidently uses it in Romans 7:23.

(13) I find then a law, that, when I would do good, evil is present with me.
(13) The conclusion: as the law of God exhorts to goodness, so does the law of sin (that is, the corruption in which we are born) force us to wickedness: but the spirit, that is, our mind, in that it is regenerated, coexists with the law of God: but the flesh, that is, the whole natural man, is bondslave to the law of sin. Therefore, in short, wickedness and death are not of the law, but of sin, which reigns in those that are not regenerated: for they neither wish to do good, neither do they do good, but they wish and do evil: but in those that are regenerated, it strives against the spirit or law of the mind, so that they cannot live at all as well as they want to, or be as free of sin as they want to.

I find then a law,.... This is to be understood either of the corruption of nature, which he found by experience to be in him; and which, because of its force, power, and prevalence it sometimes had in him, he calls "a law"; it forcibly demanding compliance with its lusts; and is the same with what he calls "evil", and which the Jews so frequently style "the evil imagination", by which they mean the corruption of nature; and one of the seven names, and the first of them, by which it is called, they tell us (k), is, "evil"; the very name it goes by here, and which they say God calls it, Genesis 6:5; and well may it be so called, since it is originally, naturally, and continually evil; it is evil in its nature and consequences; it is the source and spring of all evil:
that when I would do good; says the apostle, as soon as any good thought arises in me, any good resolution is entered into by me, or I am about to do anything that is good,
evil, the vitiosity of nature,
is present with me, and hinders me; it came into the world with me, and it has continued with me ever since; it cleaves close unto me, it lies very nigh me, and whenever there is any motion to that which is good, it starts up, which seemed to lie asleep before, and exerts itself, so that I cannot do the good I would. The Jews say (l), there are , "two hearts" in man, the good imagination, and the evil imagination. The apostle here speaks as of two wills in regenerate men, one to good, and another to evil: or this may be understood of the law of God, which he found agreed with his mind, willing that which is good, though sin lay so near to him; or he found that willing that which was good was the law of God, very agreeable to it; and that the law was on his side, favouring him, encouraging him to that which is good, though sin kept so close to him; to which sense agree the following words.
(k) T. Bab. Succa, fol. 52. 1. & Kiddushin, fol. 30. 2. (l) Tzeror Hammor, fol. 135. 4.

I find then a law - An inward constraining power, flowing from the dictate of corrupt nature.