Herman Witsius on the utility of holiness for the believer

The following excerpt is from chapter 16 of Conciliatory or Irenical Animadversions,
by Herman Witsius (1636–1708).

That is it not inconsistent we live to Christ, and consult our own advantage

V. It is certain indeed that the true Christian lives to Christ, that is, to his glory; but it does not follow from thence that he does nothing for his own advantage. It is not contrary to the duty of a holy man, to desire life, long days, and enjoy good (Ps. 34:13). Nor did Eliphaz the Temanite advise Job amiss: "pray, acquaint thyself with him, and be at peace: whereby good shall come unto thee" (Job 22:21). Nor is it unlawful to anticipate how good it shall be for me if I live to Christ." It is good for me, to draw near to God" (Ps. 73:28).

That we must do good because we live, and that we may live

VI. In fine, it is not inconsistent to do something from this principle, because we live, and to the end, that we may live. No man eats indeed but he lives, but he also eats that he may live. We both can and ought to act in a holy manner, because we are quickened by the Spirit of God. But we must also act in the same manner, that that life may be preserved in us, may increase, and at last terminate in an uninterrupted and eternal life. Moses said excellently of old, Deut. 30:19-20, "I call heaven and earth to record this day against you, that I have set life and death before you: therefore choose life, that thou mayest live, in loving the Lord thy God, obeying his voice, and cleaving unto him, for he is thy life." Deut. 7:1, "Observe to do, that ye may live." And [Deut.] 30:6, "The Lord thy God will circumcise thine heart to love the Lord thy God, that thou mayest live." Truly these speeches are not legal, but evangelical.

That it is good and holy that in the study of good works we have a regard also to our own salvation
VII. Secondly, a mercenary baseness is certainly unworthy of the high born sons God; but their heavenly Father does not forbid them to have any regard to their own advantage in the exercise of holiness. He not only permits, but also willeth "that by a patient continuance in well-doing, we seek for glory, and honour, and immortality;" and to them who do so, he will render eternal life (Rom. 2:6-7). And though he requires us to love him above all, yet he does not command that all love to ourselves be entirely banished. For we are not bound to love our neighbour, and not to love ourselves. It is also just that the study of holiness be excited in us by this love to ourselves. For, pray, what is the end of all these promises, whereby God hath commended his precepts to us, but that stimulated with a desire after them, we might the more cheerfully obey him? Not to love the benefits promised, is to contemn the goodness of God who promiseth. Not to be animated to piety through a desire after them, is to abuse them to a purpose quite opposite to that for which they were designed of God. David himself confessed that the precepts of God were far more desirable than gold, yea, than fine gold; and sweeter than honey, and the honey-comb, even on that account, because in keeping them there is great reward" (Ps. 19:10-11). And the faith of Moses is commended "because he had respect to the recompence of the reward" (Heb. 11:26). Yea, that faith is required of all who "come unto God, whereby they must believe that he is the rewarder of them who diligently seek him" (v. 6).

Provided that love to ourselves be properluy subordinate to the love of God
VIII. But at the same time this love to ourselves ought to flow from the love of God, be subordinate, and referred to it. It is not lawful to love God for our own sake, so as to consider ourselves as the end, and him as the means, by the enjoyment of whom we are rendered happy. But since we are the property of God, whom we ought to love above all. things, therefore we are also bound to love ourselves in relation to him. Our good is therefore to be sought, that in it we may taste the sweetness of the Lord, and that his peculiar treasure may be so much the more increased. Thus love to ourselves shall at last be absorbed in the ocean of love Divine. The subject itself obliges me to repeat here what I observed elsewhere.

That godliness is profitable to all things
IX. Thirdly, neither is it agreeable to the perpetual tenor of the Scriptures, that we reap no real advantage from duties rightly performed; that no evil is averted by prayers, fastings, and penitence; and that neither peace of conscience, nor joy of heart, are promoted by the exercise of virtue. Certainly this is contrary to the Mosaic doctrine, Deut. 6:18, "Do that which is right, that it may be well with thee." Add verse 3: "He who followeth after righteousness and mercy, shall find life;" "righteousness, and honour,” saith the writer of the Proverbs, chap. 21:21. Paul tells us that "godliness is great gain, and that it is profitable unto all things, having the promise of the life that now is, and of that which is to come" (1 Tim 4:8), and that "good works are good and profitable unto men" (Titus 3:8). [Witsius also references 1 Tim. 6:6, "But godliness with contentment is great gain."]

That by it impending calamities are avoided, and peace of conscience and joy promoted

X. That impending calamities are averted by penitence, is taught of God, Jer. 18:7-8 ["At what instant I shall speak concerning a nation, and concerning a kingdom, to pluck up, and to pull down, and to destroy it; if that nation, against whom I have pronounced, turn from their evil, I will repent of the evil that I thought to do unto them."]. And remarkable is Zephaniah's speech, chap. 2:3, "Seek the Jehovah, all the meek of the earth, who work his judgment, seek righteousness, seek meekness, it may be ye shall be hid in the day of Jehovah's anger.” Further, it is written in Isaiah, chap. 32:17, "That the work of righteousness shall be peace, and the effect of righteousness, quietness and assurance for ever." In the same prophet we are also taught, that if any "cease to do evil, and learn to do well, it shall come to pass that their sins, though as scarlet, shall be white as snow; and though red like crimson, they shall be as wool," chap. 1:16-18. He also teaches "that if any man rightly observed the Sabbaths of the Lord, he should delight himself in the Lord," chap. 58:13-14. 

When we believe the Scripture asserting all these things, we do not believe that the exercises of virtue or religion merit any such thing, or that the efficacy of these duties is so great, that of themselves, setting aside the divine blessing, they can procure benefits, or avert calamities: but we believe, so great is the goodness of our heavenly Father, that for Christ's sake, he liberally rewards the sincere endeavours of his children, who rejoice to please him. "For God is not unrighteous to forget your work and labour of love, which ye have shewed toward his name" (Heb. 6:10).