Matthew Poole and continuators on 2 Chronicles 35:21

21 But he sent Embassadors to him, saying, What have I to do with thee, thou king of Judah? I come not against thee this day, but against the house wherewith I have war : for God commanded me to make hast: forbear thee from meddling with God, who is with me, that he destroy thee not.

Heb. against the house or family of my war; i. e. Against the House of the King of Assyria, between whom and me there is War.

Either his False God by their lying Priests: Or the True God either 1. by some Prophet: For Gods Prophets used sometimes to deliver or send Commands from God to Heathen Kings. Though it is not probable either that Pharaoh would regard the Command of the True God: Or that a Prophet of the Lord would not acquaint Josiah with this Message: Or that Josiah would oppose Pharaoh in a War undertaken by Gods Command. Or rather 2 by a Dream, as God spoke to another Heathen King, Abimelech, Gen. 20. 3. Though it is not impossible that he pretended this for his own Advantage, that Josiah might not assist his Enemies.

Marginal references: Heb. the house of my war.