Bay'ah is a type of agreement or promise between two people. It is used in many different cultures and religions. For example, in the Muslim religion, Bay'ah is a vow or promise of loyalty made by a believer to a leader, like a King or Caliph. In other cultures, it is used to make a promise between two people, such as when a couple getting married makes a promise to love and honor each other. In all cases, Bay'ah is a special and sacred agreement between two people.