Verse 5. Remember his marvellous works that he hath done. Memory is never better employed than upon such topics. Alas, we are far more ready to recollect foolish and evil things than to retain in our minds the glorious deeds of Jehovah. If we would keep these in remembrance our faith would be stronger, our gratitude warmer, our devotion more fervent, and our love more intense. Shame upon us that we should let slip what it would seem impossible to forget. We ought to need no exhortation to remember such wonders, especially as he has wrought them all on the behalf of his people.
From The Treasury of David by Charles Spurgeon. Spurgeon's own comments on Psalm 105 verse 5.