What spiritual significance is attached to the sequence in which God instructs Elijah to anoint first Hazael, then Jehu then Elisha? (1 Kings 19:15-16) Why a heathen king of Syria first, before two of God's own people?
The reason for the order is given in the next verse:
17 And it shall come to pass, that him that escapeth the sword of Hazael shall Jehu slay; and him that escapeth the sword of Jehu shall Elisha slay.
This is later what happened. The Kings Joram & Ahazia went to war war with Hazael, king of Syria (2Ki 8:26-29). After Joram got wounded in the battle, Jehu killed both kings (2Ki 9:23-28) and the whole house of Ahab.