My heart is smitten, and dried up like grass Here he employs a third similitude, declaring that his heart is withered, and wholly dried up like mown grass. But he intends to express something more than that his heart was withered, and his bones reduced to a state of dryness. His language implies, that as the grass, when it is cut down, can no longer receive juice from the earth, nor retain the life and rigor which it derived from the root, so his heart being, as it were, torn and cut off from its root, was deprived of its natural nourishment. The meaning of the last clause, I have forgotten to eat my bread, is, My sorrow has been so great, that I have neglected my ordinary food. The Jews, it is true, during their captivity in Babylon, did eat their food; and it would have been an evidence of their having fallen into sinful despair, had they starved themselves to death. But what he means to say is, that he was so afflicted with sorrow as to refuse all delights, and to deprive himself even of food and drink. True believers may cease for a time to partake of their ordinary food, when, by voluntary fasting, they humbly beseech God to turn away his wrath, but the prophet does not here speak of that kind of abstinence from bodily sustenance. He speaks of such as is the effect of extreme mental distress, which is accompanied with a loathing of food, and a weariness of all things. In the close of the verse, he adds, that his body was, as it were, consuming or wasting away, so that his bones clave to his skin.

My heart is smitten - Broken; crushed with grief. We now speak of "a broken heart." Even death is often caused by such excessive sorrow as to crush and break the heart.
And withered like grass - It is dried up as grass is by drought, or as when it is cut down. It loses its support; and having no strength of its own, it dies.
So that I forget to eat my bread - I am so absorbed in my trials; they so entirely engross my attention, that I think of nothing else, not even of those things which are necessary to the support of life. Grief has the effect of taking away the appetite, but this does not seem to be the idea here. It is that of such a complete absorption in trouble that everything else is forgotten.

My heart is smitten, and withered like grass - The metaphor here is taken from grass cut down in the meadow. It is first smitten with the scythe, and then withered by the sun. Thus the Jews were smitten with the judgments of God; and they are now withered under the fire of the Chaldeans.

My heart is smitten, and withered like grass; so that I forget (d) to eat my bread.
(d) My sorrows were so great that I did not eat.

My heart is smitten, and withered like grass,.... Like grass in the summer solstice (d), which being smitten with the heat of the sun, or by some blast of thunder and lightning, is dried up, and withers away; so his heart was smitten with a sense of sin, and of God's wrath and displeasure at him, and with the heat of affliction and trouble, that it failed him, and he could not look up with joy and comfort:
so that I forget to eat my bread; sometimes, through grief and trouble, persons refuse to eat bread, as Jonathan and Ahab, which is a voluntary act, and purposely done; but here, in the psalmist, there was such a loss of appetite, through sorrow, that he forgot his stated meals, having no manner of inclination to food: some understand this of spiritual food, the bread of life, refusing to be comforted with it; so the Targum,
"for I forgot the law of my doctrine.''
(d) "Quasi solstitialis herba paulisper fui", Plauti Pseudolus, Acts. 1. Sc. 1. v. 36.

(Compare Psalm 121:6).
so that I forget--or, "have forgotten," that is, in my distress (Psalm 107:18), and hence strength fails.