Romans 7:21

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 (erh ruy) "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 ^F11, is, (er) , "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 ^F12, there are (twbbl ytv) , "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.