Isaiah 38:12

He tells us what his thoughts were of himself when he was at the worst; and these he keeps in remembrance, (1.) As blaming himself for his despondency, and that he gave up himself for gone; whereas while there is life there is hope, and room for our prayer and God's mercy.

He plainly expects to exist, and not cease to be in another state; as the shepherd still lives, after he has struck his tent and removed elsewhere. I have cut off--He attributes to himself that which is God's will with respect to him; because he declares that will. So Jeremiah is said to "root out" kingdoms, because he declares God's purpose of doing so (Jer 1:10).

The prayer and thanksgiving song of Hezekiah is only given here, not in the parallel passages of Second Kings and Second Chronicles. Isa 38:9 is the heading or inscription.

Mine age - The word which is used here (דור dôr) means properly the revolving period or circle of human life. The parallelism seems to demand, however, that it should be used in the sense of dwelling or habitation, so as to correspond with the ‘shepherd’s tent.’ Accordingly, Lowth and Noyes render it, ‘Habitation.’ So also do Gesenius and Rosenmuller. The Arabic word has this signification; and the Hebrew verb דור dûr also means “to dwell, to remain,” as in the Chaldee. Here the word means a dwelling, or habitation; that is, a tent, as the habitations of the Orientals were mostly tents. Is departed - (נסע nı̂ssa‛). The idea here is, that his dwelling was to be transferred from one place to another, as when a tent or encampment was broken up; that is, he was about to cease to dwell on the earth, and to dwell in the land of silence, or among the dead. From me as a shepherd’s tent - As suddenly as the tent of a shepherd is taken down, folded up, and transferred to another place. There is doubtless the idea here that he would continue to exist, but in another place, as the shepherd would pitch his tent or dwell in another place. He was to be cut off from the earth, but he expected to dwell among the dead. The whole passage conveys the idea that he expected to dwell in another state - as the shepherd dwells in another place when he strikes his tent, and it is removed. I have cut off like a weaver my life - This is another image designed to express substantially the same idea. The sense is, as a weaver takes his web from the loom by cutting the warp, or the threads which bind it to the beam, and thus loosens it and takes it away, so his life was to be cut off. When it is said, ‘I cut off’ (קפדתי qipadetiy), the idea is, doubtless, I AM cut off; or my life is cut off. […]