Those whom God, according to His purpose, calls to the communion of His Son, our Lord Jesus Christ, and regenerates by the Holy Spirit, He also delivers from the dominion and slavery of sin, though in this life He does not deliver them altogether from the body of sin and from the infirmities of the flesh.
Hence spring forth the daily sins of infirmity, and blemishes cleave even to the best works of the saints. These are to them a perpetual reason to humiliate themselves before God and to flee for refuge to Christ crucified; to mortify the flesh more and more by the spirit of prayer and by holy exercises of piety; and to press forward to the goal of perfection, until at length, delivered from this body of death, they shall reign with the Lamb of God in heaven.
By reason of these remains of indwelling sin, and also because of the temptations of the world and of Satan, those who are converted could not persevere in that grace if left to their own strength. But God is faithful, who, having conferred grace, mercifully confirms and powerfully preserves them therein, even to the end.
Although the weakness of the flesh cannot prevail against the power of God, who confirms and preserves true believers in a state of grace, yet converts are not always so influenced and actuated by the Spirit of God as not in some particular instances sinfully to deviate from the guidance of divine grace, so as to be seduced by and to comply with the lusts of the flesh; they must, therefore, be constant in watching and prayer, that they may not be led into temptation. When these are neglected, they are not only liable to be drawn into great and heinous sins by the flesh, the world, and Satan, but sometimes by the righteous permission of God actually are drawn into these evils. This, the lamentable fall of David, Peter, and other saints described in Holy Scripture, demonstrates.
By such enormous sins, however, they very highly offend God, incur a deadly guilt, grieve the Holy Spirit, interrupt the exercise of faith, very grievously wound their consciences, and sometimes for a while lose the sense of Gods favor, until, when they change their course by serious repentance, the light of Gods fatherly countenance again shines upon them.