Al-Khidr

A mysterious, mystical figure in popular
and Sufi legend, who is said to be the
unnamed sage in the 18th chapter
of the Qur'an who instructs Moses in
esoteric wisdom. When Moses goes on a
journey in search of the confluence of
the “two rivers,” he and his companion
find that they have forgotten a fish they
had for provisions; the fish finds its way
into the water, comes back to life, and
swims away. While searching for the
fish, they encounter the unnamed figure
who agrees to instruct Moses in wisdom
if he can refrain from challenging his
actions. Moses promises, but is ultimately
unable to keep from asking
about the esoteric actions that seem
wrong or contradictory in the exoteric
world. As a result, Al-Khidr is understood
as the master of esoteric wisdom
and is credited as the founder of many
Sufi orders. Many scholars, particularly
in the West, have remarked on the
parallels between the story of al-Khidr
and the Alexander Romance, which is
itself derived from the story of Gilgamesh.
In popular stories, al-Khidr often appears
in the guise of a beggar or some
other unlikely person and rewards the
person who gives charity and punishes
the person who acts selfishly.

from "A Concise Encyclopedia Of Islam" by Gordon Newby