He hath also broken my teeth with gravel stones, he hath covered me with ashes. He hath ... broken my teeth with gravel - referring to the grit that often mixes with bread baked in ashes, as is the custom of baking in the East (Proverbs 20:17). We fare as hardly as those who eat such bread. The same allusion is in "covered me with ashes" - namely, as bread is covered over.
Verse 17. I forgat prosperity. Not only present, but all hope of future prosperity, is removed; so much so, that I am as one who never was prosperous ("I forgat prosperity"). Verse 18. My hope is perished from the Lord - i:e., my hope derived from Him is perished (Psalms 31:22). [Zayin (z)]