All they that be fat upon the earth - The general meaning of this verse is, that “all classes of persons” will come and worship the true God; not the poor and needy only, the afflicted, and the oppressed, but the rich and the prosperous. There are three classes mentioned as representing all:
(1) the rich and prosperous;
(2) they who bow down to the dust, or the crushed and the oppressed;
(3) those who are approaching the grave, and have no power to keep themselves alive.
The first class comprises those who are mentioned here as being fat. This image is often used to denote prosperity: Judges 3:29; Job 15:27; Psalms 17:10; Psalms 73:4 (Hebrew); Deuteronomy 31:20; Deuteronomy 32:15. The meaning is, that the rich, the great, the prosperous would be among the multitudes who would be converted to the living God.
Shall eat and worship - This expression is derived from the custom of offering sacrifices, and of feasting upon portions of the animal that was slain. In accordance with this, the blessings of salvation are often represented as a “feast” to which all are invited. See the notes at Isaiah 25:6. Compare Luke 14:16.
All they that go down to the dust - All those descending to the dust. Those who are bowed down to the dust; who are crushed, broken, and oppressed; the poor, the sad, the sorrowful. Salvation is for them, as well as for the rich and the great.
Shall bow before him - Shall worship before the true God.
And none can keep alive his own soul - Or rather, and he who cannot keep his soul (that is, himself) alive. So the Hebrew properly means, and this accords better with the connection. The class here represented is composed of those who are ready to perish, who are about to die - the aged - the infirm - the sick - the dying. These, thus helpless, feeble, and sad, shall also become interested in the great plan of salvation, and shall turn unto the Lord. These classes would represent all the dwellers on the earth; and the affirmation is equivalent to a statement that men of all classes would be converted, and would partake of the blessings of salvation.