For when we were in the flesh, the motions of sins, which were by the law, did work in our members to bring forth fruit unto death. For, when we were in the flesh - When we were without the Gospel, in our carnal and unregenerated state, though believing in the law of Moses, and performing the rites and offices of our religion.
The motions of sins, which were by the law - Τα παθηματα των ἁμαρτιων, the passions of sins, the evil propensities to sins; to every particular sin there is a propensity: one propensity does not excite to all kinds of sinful acts; hence the apostle uses the plural number, the Passions or propensities of Sins; sins being not more various than their propensities in the unregenerate heart, which excite to them. These παθηματα, propensities, constitute the fallen nature; they are the disease of the heart, the pollution and corruption of the soul.
Did work in our members - The evil propensity acts εν τοις μελεσιν, in the whole nervous and muscular system, applying that stimulus to every part which is necessary to excite them to action.
To bring forth fruit unto death - To produce those acts of transgression which subject the sinner to death, temporal and eternal. When the apostle says, the motion of sin which were by the law, he points out a most striking and invariable characteristic of sin, viz. its rebellious nature; it ever acts against law, and the most powerfully against known law. Because the law requires obedience, therefore it will transgress. The law is equally against evil passions and evil actions, and both these exert themselves against it. So, these motions which were by the law, became roused into the most powerful activity by the prohibitions of the law. They were comparatively dormant till the law said, thou shalt Not do this, thou shalt Do that; then the rebellious principle in the evil propensity became roused, and acts of transgression and omissions of duty were the immediate consequences.