Charles H. Spurgeon on Psalms 89:52

Blessed be the Lord for evermore. Amen, and Amen. Victory begins to shine in the phrase, Blessed be Jehovah for evermore. Amen, and Amen. Some think that these words are not the words of the Psalmist, because they are of opinion that they do not agree with the preceding, but were written by another, or added by the Collector of the Psalms as a concluding doxology; or if the Psalmist wrote them, he did so merely in finishing his prayer. But it is a matter of the greatest moment; for it indicates the victory of faith, since he observes that after that grief, the reproach of the heel is gloriously removed that the Messiah may remain a victor for ever, having bruised the serpent's head, and taken away from him in perpetuity all his power of hurting. That this should certainly take place, he adds the seal of faith again and again: "Amen, and Amen." —James Alting, 1618-1679.