Charles H. Spurgeon on Psalms 16:9

"Therefore my heart is glad," etc. That is, I am all over in very good plight, as well as heart can wish, or require; I do over-abound exceedingly with joy; "God forgive me mine unthankfulness and unworthiness of so great glory" (as that martyr said): "In all the days of my life I was never so merry as now I am in this dark dungeon," etc. Wicked men rejoice in appearance, and not in heart (2 Corinthians 5:12); their joy is but skin deep, their mirth frothy and flashy, such as wetteth the mouth, but warmeth not the heart. But David is totus totus, quantus quantus exultabundus; his heart, glory, flesh, (answerable, as some think to that of the apostle, 1 Thessalonians 5:23; spirit, soul, and body) were all overjoyed. —John Trapp.