Blessed be the LORD God of Israel from everlasting, and to everlasting. {k} Amen, and Amen.

(k) By this repetition he stirs up the faithful to praise God.

Wesley's Notes

41:13 Amen - Signifies an hearty assent and approbation, and withal an earnest desire of the thing, to which it is annexed. And as the psalms are divided into five books, so each of them is closed with this word; the first here: the second, Psal 72:19, the third, Psal 89:52, the fourth, Psal 106:48, the last in the end of Psal 150:6, the doubling of the word shews the fervency of his spirit, in this work of praising God.

Jamieson-Fausset-Brown Bible Commentary

13. Blessed-praised, usually applied to God. The word usually applied to men denotes happiness (Ps 1:1; 32:1). With this doxology the first book closes.

Matthew Henry's Concise Commentary

41:5-13 We complain, and justly, of the want of sincerity, and that there is scarcely any true friendship to be found among men; but the former days were no better. One particularly, in whom David had reposed great confidence, took part with his enemies. And let us not think it strange, if we receive evil from those we suppose to be friends. Have not we ourselves thus broken our words toward God? We eat of his bread daily, yet lift up the heel against him. But though we may not take pleasure in the fall of our enemies, we may take pleasure in the making vain their designs. When we can discern the Lord's favour in any mercy, personal or public, that doubles it. If the grace of God did not take constant care of us, we should not be upheld. But let us, while on earth, give heartfelt assent to those praises which the redeemed on earth and in heaven render to their God and Saviour.