"For the flesh lusts against the Spirit, and the Spirit against the flesh--and these are contrary the one to the other--so that you cannot do the things that you would." Galatians 5:17
The Holy Spirit is especially tender of his own work upon the soul. He originally formed it--it is his own spiritual offspring; and as a mother watches over her babe, so the blessed Spirit watches over the spirit of his own creating. It is the counterpart of himself, for it is the spirit that he has raised up in the soul by his own almighty power. He, therefore, acts upon it, breathes into it fresh life and power, and communicates grace out of the inexhaustible fullness of the Son of God, thus enabling the spirit to breathe and act, struggle and fight against the flesh, so that the latter cannot have all its own way, but must submit and yield. For the spirit can fight as well as the flesh; can act as well as the flesh; and can desire good as well as the flesh can desire evil.
What a mercy for us it is that there are those heavenly breathings in our soul, of the spirit against the flesh, cryings out to God against it; and that the spirit within us thus takes hold of the arm of Omnipotence outside us, seeks help from the Lord God Almighty, and by strength thus communicated fights against the flesh, and gains at times a most blessed victory over it. For what can the flesh do against the spirit when animated by divine power? What are sin, Satan, and the world when they have to oppose a Triune God in arms? This makes the victory sure, that our friends are stronger than our foes, and the work of God upon our soul greater than anything sin, Satan, or the world can bring against it. This made the Apostle say, after he had been describing the inward conflict, "I thank God through Jesus Christ our Lord" (Rom. 7:25). And when he had enumerated the opposition that the Christian has to endure on every side, he cries out, as if in holy triumph, "No, in all these things we are more than conquerors through him who loved us" (Rom. 8:37).