Charles H. Spurgeon on Psalms 53:2

That did seek God. Although all things are full of God, yet is he to be sought for of godly men, by reason of the darkness which compasseth our minds through original sin. For both the flesh, and the senses, and earthly affections do hinder us from knowing of him, yea, though he be present. Peter Martyr, 1500-1562.

Verses 2-3. Their sin is described in gradation. They do not understand, because a true knowledge of things divine forms the basis of proper conduct towards God; they do not ask for God, because they only care for him whose clear and sure insight apprehends him as their highest possession; they are gone aside, because he who cares not for him is sure to get estranged from him, and to deviate from his paths; and they are altogether become filthy (i.e., worthless), because man's proper strength and fitness for virtue must well from the fountain of communion with God. Agustus F. Tholuck.