The basic system of "the journey in search of knowledge" that developed early in Hadith scholarship, involved travelling to specific authorities (''shaykhs''), especially the oldest and most renowned of the day, to hear from their own mouths their hadiths and to obtain their authorization or "permission" (''ijazah'') to transmit those in their names. This ijazah system of personal rather than institutional certification has served not only for Hadith, but also for transmission of texts of any kind, from history, law, or philology to literature, mysticism, or theology. The ''isnad'' of a long manuscript as well as that of a short hadith ideally should reflect the oral, face-to-face, teacher-to-student transmission of the text by the teacher's ijazah, which validates the written text. In a formal, written ijazah, the teacher granting the certificate typically includes an isnad containing his or her scholarly lineage of teachers back to the Prophet through Companions, a later venerable shaykh, or the author of a specific book.