Bay'ah (Arabic: بَيْعَة, literally to sell), in Islamic terminology, is an oath of allegiance to a leader. It is known to have been practiced by the Islamic prophet Muhammad. Bay'ah is sometimes taken under a written pact given on behalf of the subjects by leading members of the tribe with the understanding that as long as the leader abides by certain requirements towards his people, they are to maintain their allegiance to him. Bay'ah is still practiced in countries such as Saudi Arabia and Sudan. In Morocco, Bay'ah is one of the foundations of the Monarchy. In many Islamic traditions, the meaning of bay'ah is to sell ones self to a spiritual master, pir or sheikh in exchange for the spiritual knowledge which he gives.

The tradition of bay'ah can be traced back to the era of Muhammad. From the beginning bay'ah was taken by Muhammad as an oath of allegiance. Anybody who wanted to enter Islam did so by reciting the basic statement of the faith expressing his faith in the oneness of God and the prophethood of Muhammad. In addition to this the prophet formally took bay'ah from the people and tribes. Through this formal act they entered the Islamic community and showed their willingness to follow and obey Muhammad. The wordings of the oath differ in different traditions but it contains the shahada and prayers of repentance.

A bay is a large body of water connected to an ocean or sea formed by an inlet of land due to the surrounding land blocking some waves and often reducing winds. Bays also exist as an inlet in a lake or pond. A large bay may be called a gulf, a sea, a sound, or a bight. A cove is a circular or oval coastal inlet with a narrow entrance; some coves may be referred to as bays.

Bays were significant in the history of human settlement because they can provide a safe place for fishing. Later they were important in the development of sea trade as the safe anchorage they provide encouraged their selection as ports. Any bay may contain fish and other sea creatures or be adjacent to other bays. For example, James Bay is adjacent to Hudson Bay. Large bays, such as the Bay of Bengal and the Hudson Bay, have varied marine geology.

There are various ways that bays can be created. The largest bays have developed as a result of continental drift. As the super-continent Gondwana broke up along curved and indented fault lines, the continents moved apart and the world's largest bays formed. These include the Gulf of Guinea, Persian Gulf, Gulf of Alaska, Gulf of Mexico and the Bay of Bengal which is the largest bay in the world.

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]}