Khidr the Prophet
Khidr is a prophet. He is best known for his appearance in the Qur'an in chapter Kahf.[Qur'an 18:65] Although not mentioned by name in the verse. Islamic tradition sometimes describes Khiḍr as “Tutor of the Prophets”, for the spiritual guidance he has shown every prophet who has appeared throughout history. The one prophet whom Khiḍr did not teach is Muhammad; significantly, it is Muhammad who taught Khiḍr. Khiḍr is believed to be a man who has the appearance of a young adult but a long, white beard. who disappeared after being in the lake ####regions of Sijistan or Sistan that comprise the wetlands of the Iran-Afghan border today, and after finding the fountain of life, sought to live his entire remaining life in service of God and to help those in their path/journey to Him
Quranic narrative
In verse 18:65-82, Moses meets al-Khiḍr, referred in the Quran as "one from among Our servants whom We had granted mercy from Us and whom We had taught knowledge from Ourselves,"[Qur'an 18:65] at the junction of the two seas and asks for permission to accompany him so Moses can learn "right knowledge of what [he has] been taught".[Qur'an 18:66]. Khiḍr got his name after he was present over the surface of some ground that became green as a result of his presence there. It is said that Khiḍr was present at the funeral of Prophet Muhammad.
In Sufism
To Sufis, Khiḍr holds a very dear place. Although amongst the Sunni scholars there is a difference of opinion about him being still alive, amongst Sunni Sufis there is almost a consensus that al-Khiḍr is still alive. In Sufi tradition, Khiḍr has come to be known as one of those who receive illumination direct from God without human mediation.
Sources :
wikipedia