John Calvin Commentary Psalms 102:9

"For I have eaten ashes like bread, And mingled my drink with weeping," — Psalms 102:9 (ASV)

For I have eaten ashes like bread. Some think that the order is inverted here, and that the letter כ, caph, the sign of comparison, which is put before לחם, lechem, the word for bread, should be placed before אפר, epher, the word for ashes; as if it had been said, I find no more relish for my bread than I do for ashes, and the reason is that sorrow of heart produces loathing of food.

But the simpler meaning is that, lying prostrate on the ground, they licked, as it were, the earth, and so ate ashes instead of bread. It was customary for those who mourned to stretch themselves at full length with their faces on the ground. The prophet, however, intended to express a different idea—to intimate that when he ate his meals, no table was set before him, but his bread was thrown to him on the ground in a foul and disgusting manner. Speaking, therefore, as the faithful, he asserts that he was so fixed to the ground that he did not even rise from it to take his food. The same sentiment is expressed in the last part of the verse, I have mingled my drink with weeping; for while mourners usually restrain their sorrow during the short time in which they refresh themselves with food, he declares that his mourning was continuous. Some, instead of reading in the first clause, as bread, read, in bread; and as the two letters, כ, caph, and ב, beth, nearly resemble each other, I prefer reading in bread, which agrees better with the second clause.