Galatians 5:18

"But if you are led by the Spirit." If, he says, you walk according to the will of the Holy Spirit, you will not go astray. But the one who does not stumble in anything does not need the law and its guidance that follows …

He did not say "Walk in the Spirit so that you will not have desires of the flesh" but "so that you will not gratify them." Not to have them at all, indeed, is not the struggle but the prize of struggle, if we shall have obtained the victory by perseverance under grace. For it is only the transformation of the body into an immortal state that will no longer have desires of the flesh.

A person is "under the law" when he is conscious of abstaining from works of sin through fear of the torments threatened by the law rather than by love of righteousness. He is not yet free, not yet a stranger to the will to sin. For he does wrong by his very willing, since he would prefer if it were possible that there should be nothing for the will to fear, so that he might do freely what he secretly desires.… By the law which he has used to instill fear [God] has not imparted love. Godly love is suffused in our hearts not through the letter of the law but through the Holy Spirit, which is given to us.

The holy prophets and Moses, walking in the Spirit and living in the Spirit, were not under the law. But they lived as if under the law, so that they appeared indeed to be under the law, but only in order to benefit those who were under the law and spur them on from the lowliness of the letter toward the heights of the Spirit.

If it be asked in what way are these two connected, I answer, closely and plainly; for he that hath the Spirit as he ought, quenches thereby every evil desire, and he that is released from these needs no help from the Law, but is exalted far above its precepts. He who is never angry, what need has he to hear the command, Thou shalt not kill? He who never casts unchaste looks, what need hath he of the admonition, Thou shalt not commit adultery? Who would discourse about the fruits of wickedness with him who had plucked up the root itself? for anger is the root of murder, and of adultery the inquisitive gazing into faces. Hence he says, "If ye are led by the Spirit, ye are not under the Law;" wherein he appears to me to have pronounced a high and striking eulogy of the Law, if, at least, the Law stood, according to its power, in the place of the Spirit before the Spirit's coming upon us. But we are not on that account obliged to continue apart with our schoolmaster. Then we were justly subject to the Law, that by fear we might chasten our lusts, the Spirit not being manifested; but now that grace is given, which not only commands us to abstain from them, but both quenches them, and leads us to a higher rule of life, what more need is there of the Law? He who has attained an exalted excellence from an inner impulse, has no occasion for a schoolmaster, nor does any one, if he is a philosopher, require a grammarian. Why then do ye so degrade yourselves, as now to listen to the Law, having previously given yourselves to the Spirit?