Hushai was a friend and supporter of King David. During Absalom’s rebellion (2 Sam 15:30). Hushai expressed his sorrow over David’s exile by tearing his clothes (Gen 37:34) and throwing dust on his head.
Adam, the first man, was created by the Lord from “the dust of the ground” (Gen 2:7), one of the most common substances on earth. Putting dust on one’s head may have been a way of showing humility and helplessness in the face of sorrow.
The custom of putting dust on the head is also referred to in several other passage in the Bible (Joshua 7:6; 1 Samuel 4:12; 2 Samuel 1:2; 13:19; Nehemiah 9:1; Job 2:12; Lementations 2:10; Ezekiel 27:20; Revelation 18:19).
2 SAMUEL 15:32 – Hushai the Archite came to meet him [David] with his coat rent [torn, NIV], and earth [dust, NIV] upon his head.