Being confident of this very thing,.... The reason of his thanksgiving, and of his making request with joy continually on the behalf of this church, was the confidence and full persuasion he had of this same thing, of which he could be as much assured as of any thing in the world:
that he which hath begun a good work in you, will perform it until the day of Jesus Christ: by this good work is not meant the preaching of the Gospel among them, nor a Gospel church state set up in the midst of them: for though the preaching of the Gospel was a good work, and issued well in the conversion of many, in their edification and comfort, and which was still continued; and though a Gospel church state was erected among them, and was now flourishing, yet the apostle could not assure himself of the continuance of either of them, especially until the day of Christ; and both have been removed from thence many hundreds of years ago: nor is their liberal communication to the support of the Gospel intended; for though this was a good work, yet this was not wrought by God, but by themselves, and was not wrought in them, but done by them; nor their good lives and conversations. The Syriac version indeed renders it "good works", but these cannot be designed, for the same reasons as before; for though they are good things, and answer many valuable ends and purposes, yet they are external works done by men, and not internal ones wrought in them by God; wherefore by it is undoubtedly meant the work of grace upon their hearts, sometimes called the work of faith, because that is a principal part of it: this is God's work, and not man's, as may be concluded from the nature of the work itself, which is the transforming of a man by the reviewing of him, a regeneration, a resurrection, and a creation, and therefore requires almighty power; and from the condition man is in by nature, he is dead in sin, and has no power to act spiritually, and much less what is equal to such a work as this; he has no will, desire, and inclination to it, but all the reverse; and if he had, he could no more effect it, than the dry bones in Ezekiel's vision could cause themselves to live. This is the work of God. Sometimes it is ascribed to the Father, who regenerates, calls by his grace, reveals his Son, and draws souls unto him; and sometimes to the Son, who quickens whom he will, whose Spirit is given, whose image is stamped, and out of whose fulness grace is received; but more commonly it is attributed to the Spirit, who is a spirit of regeneration, sanctification, and faith: and this is a "good work", as it must needs be, since it is God's work; he is the efficient cause of it; his good will and pleasure, his grace and mercy are the moving cause of it, and not men's works; and his good word is the means of it. The matter of it is good; it is an illumination of the understanding, a subduing of the will, a taking away of the stony heart, and a giving of an heart of flesh, an infusion of spiritual life, a formation of Christ in the soul, and an implantation of all grace there: it is good in its effects; it makes a man a good man, and fits and qualifies him to perform good works, which without it he cannot do; it makes a man a proper habitation for God, and gives him meetness for the heavenly inheritance. And this is an internal work, a work begun "in" the saints; nothing external is this work; not an outward reformation, which, when right, is the fruit of this good work; nor external humiliation for sin; nor a cessation from the grosser acts of sin; nor a conformity and submission to Gospel ordinances; all which may be where this work is not; but it is something within a man; as appears from the names by which it goes; such as spirit, so called, because it is of a spiritual nature, wrought by the Spirit of God, and has its seat in the spirit of man; it is called the inward man, which is renewed day by day; a seed that remains in him, and a root which is out of sight, and oil in the vessel, the heart, as distinct from the lamp of an outward profession: as also from the several things, which, together, make up the subject of it; it is the understanding which is enlightened; the will which is subdued; the heart and inward parts in which the laws of God are written; the mind and conscience, which are sprinkled with the blood of Christ, and cleansed; and the affections, which are set on divine objects. This is a begun work, and but a begun one. It may be said to be begun as soon as light is let into the soul by the Spirit of God; when it sees its lost state, and need of a Saviour, for as the first thing in the old creation was light, so in the new; when the fear of God is put into the heart, which is the beginning of wisdom; when love appears in the soul to God, to Christ, to his people, word, and ordinances; and when there are the seeing, venturing, and relying acts of faith on Christ, though there is a great deal of darkness, trembling, and unbelief; and when it is got thus far, and even much further, it is but a begun work; it is not yet finished and perfect: this appears from the several parts of this work, which are imperfect, as faith, hope, love, knowledge, &c. from the indwelling of sin, and corruption in the best of saints; from their various continual wants and necessities; from their disclaiming perfection in this life, and their desires after it. But the apostle was confident, and so may every good man be confident, both for himself and others, that God who has, and wherever he has begun the good work of grace, will "perform", finish it, or bring it to an end, as the word here used signifies: and this the saints may assure themselves of, from many considerations; as from the nature of the work itself, which is called living water, because it always continues, a well of it, because of its abundance, and is said to spring up to eternal life; because it is inseparably connected with it, where there is grace, there will be glory; grace is the beginning of glory, and glory the perfection of grace; this work of grace is an incorruptible seed, and which remains in the saints, and can never be lost; it is a principle of life, the root of which is hid in Christ, and that itself is maintained by him, and can never be destroyed by men or devils: and also from the concern God has in it, who is unchangeable in his nature, purposes, promises, gifts, and calling; who is a rock, and his work is perfect sooner or later; who is faithful, and will never forsake the work of his hands, and has power to accomplish it; and who has promised his people, that they shall grow stronger and stronger, that they shall not depart from him, and he will never leave them. Moreover, this may be concluded from the indwelling of the Spirit, as a spirit of sanctification, as the earnest and seal of the inheritance, and that for ever; and from the intercession and fulness of grace in Christ, and the saints' union to him, and standing in him; as well as front the impotency of any to hinder the performance of this work, as sin, Satan, or the world: to which may be added the glory of all the three Persons herein concerned; for if this work is not finished, the glory of God the Father in election, in the covenant of grace, in the contrivance of salvation, in the mission of his Son, the glory of Christ in redemption, and of the Spirit in sanctification, would be entirely lost: wherefore it may be depended on, this work will be performed wherever it is begun, and that "until the day of Jesus Christ"; meaning either the day of death, when Christ takes the souls of believers to himself, and they shall be for ever with him, when this work of grace upon the soul will be finished; for God, who is the guide of his people, will be their God and guide even unto death: or else the last day, the day of judgment, the resurrection day, when Christ shall appear and raise the dead, and free the bodies of the saints from all their bondage, corruption, vileness, and weakness, which will be putting the last and finishing hand to this good work; nor will even the bodies of the saints be quitted by the Spirit of God till this is done.