Charles Ellicott Commentary 2 Chronicles 35:21

"But he sent ambassadors 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; and God hath commanded me to make haste: forbear thee from [meddling with] God, who is with me, that he destroy thee not." — 2 Chronicles 35:21 (ASV)

But ... ambassadors. — And ... messengers.

What have I to do with thee?—Literally, what to me and to you? Τί ἐμοὶ καὶ σοί; (Septuagint; Luke 8:28).

I come not against thee. — So the old versions. The Hebrew is, “not against you—you—today.” The versions appear to have read ‘attâh, “you,” with different points as ‘ôtheh, “coming.” (Compare to Syriac, ôthê ‘nû, “I come.”)

But against the house ... war. — A strange expression. (Compare to 1 Chronicles 18:10.) Probably the reading indicated by 3 Esdras 1:25 is right (ὲπὶ γὰρ τοῡ Εὐφράτου δ πόλεμος μοῡ ἐστί), “but against the Euphrates is my war” (Perath for bêth). Josephus supports this. Septuagint and Syriac omit; Vulgate, “sed contra aliam pugno domum.”

For God ... haste. — And God ... The Egyptian kings, like those of Israel, consulted their prophets before undertaking any expedition. So did the Assyrians, as abundantly appears from their inscriptions. So, too, we read on the Moabite stone, “Chemosh said to me, Go; take Nebo ... Go up against Horonaim, and take it.” These facts sufficiently explain the text, without assuming that Necho had received an oracle from Jehovah, or was referring to the God of Israel. (Compare to Herodotus, 2.158.)