A reference to the tenth commandment (Ex. 20:17).

 Gr. epithumia, “desire,” “longing,” sometimes, for proper things (Luke 22:15; Phil. 1:23), but usually for forbidden things (Rom. 13:14; James 1:14, 15; etc.). The word for “covet” later in the verse is epithumeō, the verb form of epithumia. The relationship between the two words may be illustrated by the following translation: “I should not have known what it is to covet if the law had not said, Thou shalt not covet.” See further on Rom. 7:8, where epithumia is translated “concupiscence.”

 Literally, “through law” (see on ch. 2:12).

 Since sin is “lawlessness,” or “disobedience to law” (see on 1 John 3:4), it is only logical that the effect of law in a man’s experience should be to reveal his sin to him in its true nature. The illogical attitude toward law is to regard it as an enemy for having made this truthful exposure. A mirror is not an enemy to a homely person because it reveals to him his homeliness. Nor is a physician an enemy to someone who is sick because he discloses to him his sickness. The doctor is not the cause of the sickness, nor is the mirror the cause of the homeliness. Likewise God is not the cause of the sickness and ugliness of our sin because He shows it to us in the mirror of His holy law and by the divine Physician, who came to reveal and to heal our sinfulness.

 Gr. alla, generally translated “but,” here possibly the equivalent of “on the contrary” (see 1 Cor. 12:22). That is, far from the law being sin, on the contrary, it exposes sin. Alla may also be understood to mean “yet,” “nevertheless” (see Rom. 5:14).

That is, even though it be emphatically denied that the law is sin, nevertheless, but for the law, I would not have known sin. Either interpretation is appropriate to Paul’s argument.

 See on ch. 3:4.

 Paul has stated (v. 5) that sin makes use of the law to bring about the destruction of the sinner. Does this mean that the law itself is a sinful thing, whose only purpose is to make men worse than they were before? Paul replies by explaining that the evil is not in the law but in man. Though it is true that the law is the “occasion” of sin (v. 8), nevertheless the law itself is “holy, and just, and good” (v. 12).

 A characteristic phrase (see on ch. 4:1). Paul prepares to meet another possible misunderstanding regarding what he has said about the relationship between law and sin.

 It is significant that Paul selected the tenth commandment, for it is not merely a sample of the rest, it contains the principle that underlies all sin (see PP 309). His use of this commandment in such a context reveals a deeper meaning to it than the mere words literally express. He saw in it the prohibition not only of desire for the certain things specifically mentioned in the commandment but also of desire for anything divinely forbidden. In other words, the law prohibits any kind of selfish and sinful desire, and it was this that Paul would not have known “but by the law.” He discovered that true obedience to the commandments of God was not a mere outward conformity to the letter of law but a matter of the mind, heart, and spirit (v. 14; cf. ch. 2:29). Conversely, sin is not the mere external breach of the letter of the law, but is a deep-seated condition of mind, mood, habit, and character, from which spring the sinful acts (see Matt. 5:28; 1 John 3:15). However, the initial effect of this profound discovery on Paul’s unregenerate heart was to stir up his corrupt nature to sinful opposition (Rom. 7:8).