Khidr "the Green One", also transcribed as Khidar, Khizr, Khyzer, Khizar, Kezr) is a revered figure in Islam, whom the Qur'an describes as a righteous servant of God, who possessed great wisdom or mystic knowledge, represented iconically by a fish. 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 mythical Persian king Afridun, Alexander the Great, 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.

In chapter 18, verses 65–82, Moses meets the Servant of God, referred in the Quran as "one from among Our friend whom We had granted mercy from Us and whom We had taught knowledge from Ourselves", 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". The Servant of God informs him in a stern manner that their knowledge is of different nature and that "Surely you [Moses] cannot have patience with me. And how canst thou have patience about things about which thy understanding is not complete?" Moses promises to be patient and obey him unquestioningly, and they set out together. After they board a ship, the Servant of God damages the vessel. Forgetting his oath, Moses says, "Have you made a hole in it to drown its inmates? Certainly you have done a grievous thing." The Servant of God reminds Moses of his warning, "Did I not say that you will not be able to have patience with me?" and Moses pleads not to be rebuked.

Hamza Yusuf Hanson is an American Islamic scholar, and (with Zaid Shakir and Hatem Bazian) is co-founder of Zaytuna College in Berkeley, California, United States. He is a convert to Islam, and is one of the signatories of A Common Word Between Us and You, an open letter by Islamic scholars to Christian leaders, calling for peace and understanding. He has described the 9/11 attacks as "an act of 'mass murder, pure and simple'". Condemning the attacks, he has also stated "Islam was hijacked ... on that plane as an innocent victim".The Guardian newspaper in the United Kingdom reported that he "is arguably the west's most influential Islamic scholar" and added that "many Muslims find his views hard to stomach."

Hamza Yusuf was born to two academics in Washington State and raised in Northern California. In 1977, he became Muslim and subsequently traveled to the Muslim world and studied for ten years in the United Arab Emirates, Saudi Arabia, as well as North and West Africa. Hamza Yusuf spent four years studying in the United Arab Emirates and elsewhere in the Middle East. Later he traveled to West Africa and studied in Mauritania, Medina, Algeria, and Morocco under such scholars as Murabit al Haaj; Baya bin Salik, head of the Islamic court in Al-'Ain, United Arab Emirates; Muhammad Shaybani, Mufti of Abu Dhabi; Hamad al-Wali; and Muhammad al-Fatrati of Al Azhar University in Cairo, Egypt.^{[citation needed]} After more than a decade abroad, he returned to the United States and earned degrees in nursing from Imperial Valley College and religious studies at San José State University.^{[citation needed]}