Q source
According to the Marcan priority, the first to be written was the Gospel of Mark (written AD 60–75), followed by the Gospel of Matthew (AD 65–85), the Gospel of Luke (AD 65–95), and the Gospel of John (AD 75–100). Most scholars agree that the authors of Matthew and Luke used Mark as a source for their gospels. Since Matthew and Luke also share some content not found in Mark, many scholars assume that they used another source (commonly called the "Q source") in addition to Mark.