Disguised himself. Compare the similar conduct of Ahab in war against Syria (1 Kings 22:30).
From the mouth of God. God speaks to man in many ways, and it is always the part of wisdom to be alert to the voice of Heaven, whether it come from layman or prophet, from one’s own countryman or from a messenger from lands afar. Of course Josiah might have justifiably questioned whether the words were of God, but he had available prophetic guidance by which the matter could be certified. In fact, he should never have gone on this venture without the approval of Heaven. By refusing to hearken to the words of Necho, Josiah refused the voice of God, and thus brought death upon himself.