It is a picture of utter destitution. The writer was driven to inner despair. In a state of complete hopelessness, he thought that it was over with him.
Following the theme of food and eating, God had given his people stones to eat. The writer had to eat pebbles because his face was trampled in the ground. His host found scornful amusement in making him eat food made of unsifted flour, or food in which pebbles were deliberately thrown (see also Proverbs 20:17).1 A different interpretation sees people scavenging for food, even scrabbling on the ground for any discarded scrap.2 Because of this, small stones were also picked up and eaten accidentally. In antiquity, sand was one of several substances which were accidentally eaten. This is evident from instances of worn-down teeth found in Egyptian mummies.3 Whatever the case and in whichever way, gravel or stones were given by God to eat as punishment for their sin (see also Psalm 102:9).
The picture of destitution continues in the second part of the verse. Two principal interpretations attempt to explain the image. The first interpretation associates the image with cultural customs of hospitality. A good host welcomes his guest by affording him the opportunity to clean himself (see Genesis 18:4); the writer was not treated in this way. He has not been given the opportunity to wash off his dust, but was humbled to the ground.4 The second interpretation associates the image with dying (see Genesis 3:19; Psalm 90:3) and suggests that the writer is close to expiring.5 In either case, the ultimate meaning stays the same: all rest and prosperity have been taken from him for good. He is feeling humiliated and hopeless. This too he recognizes as the direct act of God.
16 He has made my teeth grind on gravel, and made me cower in ashes;