Albert Barnes Commentary 2 Kings 8:15

"And it came to pass on the morrow, that he took the coverlet, and dipped it in water, and spread it on his face, so that he died: and Hazael reigned in his stead." — 2 Kings 8:15 (ASV)

A thick cloth - This was probably a cloth or mat placed between the head and the upper part of the bedstead, which in Egypt and Assyria was often shaped in such a way that pillows (in our sense) were unnecessary.

The objection that Elisha is involved in the guilt of having suggested the deed has no real force or value. Hazael was no more obliged to murder Benhadad because a prophet announced to him that he would one day be king of Syria, than David was obliged to murder Saul because another prophet anointed him king in Saul’s place (1 Samuel 16:1–13).