The Yod stanza (vv. 17, 18), like the He and Vav stanzas (vv. 7-10), passes to confidence for the future. The correspondence is very close, but the two verses of this stanza represent the four of the earlier ones; thus ver. 17 answers to vv. 7 and 8, while ver. 18 is the representative of vv. 9 and 10. In ver. 17 the "return to Sheol" is equivalent to destruction. In one view, men who cease to be may be regarded as going back to original nothingness, as in Psalm xc. 3. Sheol is not here a place of punishment, but is the dreary dwelling of the dead, from the gates of which the psalmist had been brought up. Reduction to nothingness and yet a shadowy, dim life or death-in-life will certainly be the end of the wicked. The psalmist's experience in his past deliverance entitles him to generalise thus. To forget God is the sure way to be forgotten. The reason for the certain destruction of the nations who forget God and for the psalmist's assurance of it is (ver. 18) the confidence he has that "the needy shall not always be forgotten." That confidence corresponds precisely to vv. 9, 10, and also looks back to the "hath remembered" and "not forgotten" of ver. 12. They who remember God are remembered by Him; and their being remembered--_i.e._, by deliverance--necessitates the wicked's being forgotten, and those who are forgotten by God perish. The second clause of ver. 18 echoes the other solemn word of doom from vv. 3-6. There the fate of the evil-doers was set forth as "perishing"; their very memory was to "perish." But the "expectation of the poor shall not perish." Apparently fragile and to the eye of sense unsubstantial as a soap-bubble, the devout man's hope is more solid than the most solid-seeming realities, and will outlast them all.
The final stanza (vv. 19, 20) does not take Kaph as it should do, but Qoph. Hence some critics suspect that this pair of verses has been added by another hand, but the continuity of sense is plain, and is against this supposition. The psalmist was not so bound to his form but that he could vary it, as here. The prayer of this concluding stanza circles round to the prayer in ver. 13, as has been noticed, and so completes the whole psalm symmetrically. The personal element in ver. 13 has passed away; and the prayer is general, just as the solo of praise in ver. 1 broadened into the call for a chorus of voices in ver. 12. The scope of the prayer is the very judgment which the previous stanza has contemplated as certain. The devout man's desires are moulded on God's promises, and his prayers echo these. "Let not mortal man grow strong," or rather "vaunt his strength." The word for _man_ here connotes weakness. How ridiculous for him, being such as he is, to swell and swagger as if strong, and how certain his boasted strength is to shrivel like a leaf in the fire, if God should come forth, roused to action by his boasting! Ver. 20 closes the prayer with the cry that some awe-inspiring act of Divine justice may be flashed before the "nations," in order to force the conviction of their own weakness home to them. "Set terror for them," the word _terror_ meaning not the emotion, but the object which produces it, namely an act of judgment such as the whole psalm has had in view. Its purpose is not destruction, but conviction, the wholesome consciousness of weakness, out of which may spring the recognition of their own folly and of God's strength to bless. So the two parts of the psalm end with the thought that the "nations" may yet come to know the name of God, the one calling upon those who have experienced His deliverance to "declare among the peoples His doings," the other praying God to teach by chastisement what nations who forget Him have failed to learn from mercies.