Galatians 5:17

17.For the flesh lusteth. The spiritual life maintained without a struggle. We are here informed of the nature of the difficulty, which arises from our natural inclinations being opposed to the Spirit. The word flesh, as we had occasion to observe, in expounding the Epistle to the Romans, denotes the nature of man; for the limited application of it, which the sophists make to the lower senses, as they are called, is refuted by various passages; and the contrast between the two words puts an end to all doubt. The Spirit denotes the renewed nature, or the grace of regeneration; and what else does the flesh mean, but “the old man?” (Romans 6:6, Ephesians 4:22, Colossians 3:9.) Disobedience and rebellion against the Spirit of God pervade the whole nature of man. If we would obey the Spirit, we must labor, and fight, and apply our utmost energy; and we must begin with self-denial. The compliment paid by our Lord to the natural inclinations of men, amounts to this, — that there is no greater agreement between them and righteousness, than between fire and water. Where, then, shall we find a drop of goodness in man’s free will? unless we pronounce that to be good which is contrary to the Spirit of God;

“because the carnal mind is enmity against God, for it is not subject to the law of God, neither indeed can be.”
(Romans 8:7.)

All the thoughts of the flesh are acts of enmity against God.

So that ye cannot do the things that ye would. This refers, unquestionably, to the regenerate. Carnal men have no battle with depraved lusts, no proper desire to attain to the righteousness of God. Paul is addressing believers. The things that ye would must mean, not our natural inclinations, but the holy affections which God bestows upon us by his grace. Paul therefore declares, that believers, so long as they are in this life, whatever may be the earnestness of their endeavors, do not obtain such a measure of success as to serve God in a perfect manner. The highest result does not correspond to their wishes and desires. I must again refer the reader, for a more extended view of my sentiments on this subject, to the Exposition of the Epistle to the Romans, (See Calvin on Romans 7:15.)