In ver. 16 a new turn of thought begins, which is pursued till ver. 20--namely, that of the self-retributive action of a perverted choice of evil. "He remembered not" to be gracious to him who needed compassion; therefore it is just that he should not be remembered on earth, and that his sin should be remembered in heaven. He deliberately chose cursing rather than blessing as his attitude and act towards others; therefore cursing comes to him and blessing remains far from him, as others' attitude and act to him. The world is a mirror which, on the whole, gives back the smile or the frown which we present to it. Though the psalmist has complained that he had loved and been hated in return, he does not doubt that, in general, the curser is cursed back again and the blesser blessed. Outwardly and inwardly, the man is wrapped in and saturated with "cursing." Like a robe or a girdle, it encompasses him; like a draught of water, it passes into his inmost nature; like anointing oil oozing into the bones, it steals into every corner of his soul. His own doings come back to poison him. The kick of the gun which he fires is sure to hurt his own shoulder, and it is better to be in front of the muzzle than behind the trigger. The last word of these maledictions is not only a wish, but a declaration of the Law of Divine Retribution. The psalmist could not have found it in his heart to pray such a prayer unless he had been sure that Jehovah paid men's wages punctually in full, and that conviction is the kernel of his awful words. He is equally sure that his cause is God's--because he is sure that God's cause is his, and that he suffers for righteousness and for the righteous Jehovah. The final part (vv. 21-31) returns to lowly, sad petitions for deliverance, of the kind common to many psalms. Very pathetically, and as with a tightening of his grasp, does the singer call on his helper by the double name "Jehovah, Lord," and plead all the pleas with God which are hived in these names. The prayer in ver. 21_b_ resembles that in Psalm lxix. 16, another of the psalms of imprecation. The image of the long-drawn-out shadow recurs in Psalm cii. 11. The word rendered "am I gone" occurs here only, and implies compulsory departure. The same idea of external force hurrying one out of life is picturesquely presented in the parallel clause. "I am shaken out," as a thing which a man wishes to get rid of is shaken out of the folds of a garment. The psalmist thinks of himself as being whirled away, helpless, as a swarm of locusts blown into the sea. The physical feebleness in ver. 24 is probably to be taken literally, as descriptive of the havoc wrought on him by his persecutions and trouble of soul, but may be, as often, metaphor for that trouble itself.