Is his mercy clean gone for ever? - The word rendered "clean gone" means to fail; to fail utterly. The idea is, Can it be that the compassion of God has become exhausted - that no more mercy is to be shown to mankind - that henceforth all is to be left to stern and severe justice? What would the world be if this were so! What must be the condition of mankind if mercy were no more to be shown to the race!
Doth his promise fail for evermore? - Margin, as in Hebrew, "to generation and generation." The original Hebrew rendered "promise" means "word;" and the question is, whether it can be that what God has spoken is to be found false. Can we no longer rely on what he has said? All the hopes of mankind depend on that, and if that should fail, all prospect of salvation in regard to our race must be at an end.

For evermore? - לדר ודר ledor vador, "to generation and generation." From race to race. Shall no mercy be shown even to the remotest generation of the children of the offenders?

Is his (f) mercy clean gone for ever? doth [his] promise fail for evermore?
(f) As if he would say, It is impossible: by which he exhorts himself to patience.

Is his mercy clean gone for ever?.... Or "his grace" (q); and mercy is no other than grace to objects in misery; Unbelief says it is gone, that no more will be shown, and that the treasures of it are exhausted; but Faith says it is not gone, and observes that God is the God of all grace, is rich in mercy, and abundant in goodness; that his Son is full of grace and truth, and so is the covenant; and that though there is an abundance of it given in conversion, and there are continual supplies of it afterwards; yet this grace is still sufficient, and this mercy abundant; salvation is by it, as for millions past, so for millions present and to come; the mercy of God is new every morning, it endures for ever, it is from everlasting to everlasting:
doth his promise fail for evermore? or word (r); his words of consolation, as Kimchi interprets it; the sense may be, will he speak never a word of comfort more? Unbelief says he will not, but Faith says he will; and that though he brings into the wilderness, yet he will speak comfortably there; and as he answered the Angel of the covenant with good and comfortable words, so he orders his ministers to speak, and by them he does speak comfortably to his people: or, in general, the word of the Gospel is meant; which though it may be sometimes scarce and rare, and there may be few preachers of it; yet it lives and abides for ever, it is the everlasting Gospel; or, in particular, the promise or promises of the Gospel: Faith says not one of these shall fail, grounding it upon the ability of God, and his power to perform: and upon his faithfulness, which he will never suffer to fail; and the promises of God are so far from failing for evermore, that they never fail at all; there never was any instance of any; not one of the good things which God has spoken of, from the creation of the world to this present time, have ever failed; the promises are yea and amen in Christ; see Joshua 23:14. The Targum interprets it differently of his evil word being fulfilled on every generation.
(q) "gratia ipsius", Cocceius, Gejerus. (r) "eloquim", Pagninus, Montanus; "sermo", Junius & Tremellius, Piscator; "verbum", Vatablus, Gejerus, Michaelis; "oraculum", Tigurine version, Musculus.