Dust.
Small particles of matter found on the ground, out of which man was formed, to whom it was said, "Dust thou art, and unto dust shalt thou return." Genesis 2:7; Genesis 3:19. "The first man is of the earth, earthy." 1 Corinthians 15:47. It is used as a symbol of weakness: "he remembereth that we are dust." Psalms 103:14. To 'lick the dust' is figurative of defeat. Psalms 72:9. To 'cast dust upon the head' was a sign of grief. Ezekiel 27:30; Revelation 18:19. To 'shake the dust off the feet' on leaving a city where the servants of Christ had been rejected, was leaving them to judgement: not even the dust of their city should be presented before the messengers' Master. Matthew 10:14; Acts 13:51. Similarly dust was cast or shaken into the air by men in great indignation. Acts 22:23.