In 1743 at the death of his uncle Patriarch Joseph Dergham Khazen, after the initial refusal of Simon Awad, Tobias in competition with Elias Mohasseb tried to be elected patriarch, but the case came to the Pope who chose Simon Awad in place of the two pretenders.[5][6] In 1750 Tobias was appointed bishop of Tyre and Vice-Patriarch.[2] In 1755 he was appointed Eparch of Tripoli and at the death of Simon Awad, Tobias succeeded at being elected patriarch on February 28, 1756. He was confirmed by Pope Benedict XIV on March 28, 1757.[7][8]
The new patriarch placed his residence in Kisrawan, particularly in the monastery of Mar Rouhana.
As patriarch, Tobias had three main issues to manage: the implementation of the 1736 Maronite Synod, the Hindiyya case and the problems in the Lebanese Maronite Order. To implement the 1736 Synod he summoned a new synod on August 25, 1756, without great results, and again another synod in 1762 which reduced the dioceses only to fifteen, not eight as requested in 1736. About Hindiyya he took a neutral position, which allowed Hindiyya to grow her influence during his patriarchate. The dispute over the Lebanese Maronite Order could be solved only under his successor, Joseph Estephan, when in 1770 it was divided into two branches, giving rise to OMM. Tobias El Khazen died on May 19, 1766.[7]
^[The addition of the name Peter (in Arabic : Boutros) your first name is customary for newly elected Maronite patriarchs; about El Khazen, acts Consistory of 1757 call Tobias Petrus , and likewise the patriarch signature Tobias Petrus Gazenius patriarcha Antiochenus in the letter with a request to the pope the confirmation of his election.]
^ abLeeuwen, Richard (1994). Notables and Clergy in Mount Lebanon: the Khazin Sheiks and the Maronite Church. Boston: Brill Academic Publishers. ISBN90-04-09978-6.
^[With this title is mentioned in brief cancellation of his election; see. next note.]
^de Clercq, Charles (1949). Histoire des conciles d'après les documents originaux, Tome XI Conciles des Orientaux Catholiques. Vol. 1. Paris: Letouzey et Ané. p. 274.
^ abDib, Pierre (2001). Histoire des Maronites: L'église maronite du XVIe siècle à nos jours, Volume 3. Librairie Orientale. pp. 194–196. ISBN978-9953-17-005-3.