Who is the prophet that disguised himself with ashes upon his face?

the bald Elijah

is he going to return with Jesus?

Jamieson-Fausset-Brown Bible Commentary

1Ki 20:35-42. A Prophet Reproves Him.

35-38. Smite me—This prophet is supposed (1Ki 20:8) to have been Micaiah.

The refusal of his neighbor to smite the prophet was manifestly wrong, as it was a withholding of necessary aid to a prophet in the discharge of a duty to which he had been called by God, and it was severely punished [1Ki 20:36], as a beacon to warn others (see on [321]1Ki 13:2-24). The prophet found a willing assistant, and then, waiting for Ahab, leads the king unconsciously, in the parabolic manner of Nathan (2Sa 12:1-4), to pronounce his own doom; and this consequent punishment was forthwith announced by a prophet (see on [322]1Ki 21:17)."

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Al Jolson?