Albert Barnes Commentary Acts 22:23

"And as they cried out, and threw off their garments, and cast dust into the air," — Acts 22:23 (ASV)

Cast off their clothes. Their outer garments. Probably they did it now intending to stone him (Acts 7:58).

And threw dust into the air. As expressive of their abhorrence and indignation. This was a striking exhibition of rage and vindictive malice. Paul was guarded by Roman soldiers, so that they could not injure him; and their only way of expressing their wrath was by menaces and threats, and by these tokens of furious indignation. Thus Shimei expressed his indignation against David by cursing him, and throwing stones at him, and casting dust (2 Samuel 16:13).