Charles H. Spurgeon on Psalms 118:4

God's mercy endureth for ever. That is, his covenant mercy, that precious church privilege: this is perpetual to his people, and should perpetually remain as a memorial in our hearts. And therefore it is that this is the foot or burden of these first four verses. Neither is there any idle repetition, but a notable expression of the saints' insatiableness of praising God for his never failing mercy. These heavenly birds having got a note, sing it over and over. In the last Psalm there are but six verses, yet twelve Hallelujahs. Abraham Wright.