Psalms 31:23

O love the Lord, all ye his saints
To whom his goodness extends; who are favoured with the blessings of his grace, as pardon, peace, and righteousness; and who particularly are sanctified by his Spirit, and have principles of grace and holiness wrought in their hearts: these, even all of them, are called upon to love the Lord, having that grace implanted in their souls; that is, to express it, not by words, but by deeds, under a sense of the love and kindness of God to them; and to join with the psalmist in an affectionate reverence of him, trust in him, and thankfulness to him, on account of his marvellous kindness showed him;

[for] the Lord preserveth the faithful;
such as trust in him, believe in Christ, and are faithful to his word and ordinances, abide by them, and stays near his people; these he not only preserves in a providential way, but he preserves them in a way of special grace; he keeps them "from evil", as the Targum; from the evil of sin; from a total and final falling away by it; from the evil of the world, so as not to be drawn off from Christ and his ways, either by its frowns or flatteries; and from the evil one, Satan, from being destroyed by him and his temptations; and these are preserved safe to the kingdom and glory of Christ, by the mighty power of God: some render the words, "the Lord keepeth faithfulness" ^F9; he will never suffer his own faithfulness to fail; he is a covenant keeping God, and is always true to his word and promise;

and plentifully rewardeth the proud doer;
such as all self-righteous persons are, and all that speak grievous things proudly and contemptuously against the truly righteous, ( Psalms 31:18 ) ; who bear hard upon them, and oppress them; and such as antichrist and his party, who exalts himself above all that is called God; but in what those deal proudly, God is above them, an more than a match for them, and he sets himself against them; he resists them, and will reward them according to their works.