Khidr or al-Khidr (Arabic: الخضر al-Khiḍr "the Green One", also transcribed as Khidar, Khizr, Khyzer, Khizar) is a revered figure in Islam, whom the Qur'an describes as a righteous servant of God, who possessed great wisdom or mystic knowledge. He is most often said to be a contemporary of Moses, but in other variations of his story, he lived at the same time as Abraham, the mythological Persian king Afridun and Nashiya bin Amus. The 18th sura ("The Cave") presents a narrative where Khidr accompanies Moses and tests him about his oath to not ask any questions.
In medieval Islamic tradition, Khidr is variously described as a messenger or a prophet.
Read more about Khidr: Qur'anic Narrative, Khiḍr in "The History of Al-Tabari", Reports in The Hadith, Islamic Perspectives, Comparative Mythology