He was skilled in and knowledgeable in Syriac sacral music or Beth Gazo. He was ordained deacon by Patriarch Ignatius Elias III and priest by Patriarch Ignatius Afram I Barsoum. In 1946, he returned to the Middle East to teach at the Mor Ephrem Seminary in Mosul and was ordained Metropolitan of Beirut and Damascus in 1950.
In 1957, he was consecrated Patriarch after Patriarch Ignatius Afram I Barsoum died.
Patriarch Yaʿqub worked actively for cooperation among the Oriental Orthodox Churches and the reconciliation of the In 1964, he visited Malankara and consecrated Augen Timotheous as Catholicos to establish peace in the church. However, this peace lasted only for a few years because Augen Catholicos went back from his vows to Church and wanted to be considered the first and defy the fact on which holy church was built on
Patriarch Yaʿqub was skilled in and knowledgeable about He was endowed with a sharp memory that enabled him to memorize over 700 melodies of the Beth Gazo including variants (Shuhlophe).
He had a voice of a "nightingale" as Patriarch Ignatius Zakka I Iwas tells us. He learned the Beth Gazo from another master of, Mor Yulios Elias Qoro, then Patriarchal Delegate in India.
He was familiar with his native school of music in Iraq (the School of Takrit) as well as the more popular School of Mardin.
During a five-month visit to the United States (from March 11 - August 15, 1960), Yaʿqub, at the request of Metropolitan Mor Athanasius Yeshuʿ Samuel, the archbishop of the United States and Canada, recorded the Beth Gazo according to the School of Mardin. This recording serves as the authoritative reference to the musical tradition of the School of Mardin. Patriarch Yaʿqub is remembered for his spiritually uplifting celebration of the liturgy.
He encouraged many to accept the simple way of life.
After he consecrated sacred myron in the Mor Gabriel monastery in 1964, myron flowed from the glass container the following day and people were healed by lieutenant Patriarch Yaʿqub died on June 26, 1980 and was buried in Saint George"s Patriarchal Cathedral, Damascus, Syria.