Following the resignation of Mohammad Yazdi from the powerful Guardian Council, Iranian Supreme Leader Ayatollah Ali Khamenei replaced him with another member of the clergy, Ahmad Khatami, on Sunday.
Yazdi had earlier stepped down for "old age and physical complications."
In his decree, Khamenei praised Yazdi's service as "valuable," reiterating that he resigned from his influential position for physical complications and old age.
However, the chairman of the GC, Ayatollah Ahmad Jannati, is five years older than Yazdi.
The founder of the Islamic Republic, Ayatollah Ruhollah Khomeini, appointed Yazdi as a member of the GC in 1988. A year later, Yazdi was appointed as the judiciary head, and following two five-year terms as the country's chief justice, Yazdi returned to the GC.
Born in 1931, in the central Iranian city of Isfahan, Yazdi was elected as the chairman of Iran's Assembly of Experts in 2015. Additionally, he is one of the founders and the secretary of the Society of Seminary Teachers of Qom, widely known as Shi'ites' seminaries' police.
Iranian Supreme Leader Ayatollah Khamenei is now 81 years old and has been leading Iran for 32 years.
Khatami, Yazdi's replacement, was born in 1960 in Semnan, east of the Iranian capital city, Tehran.
Khatami is currently one of Tehran's Friday Prayer Imam and a member of the Assembly of Experts presidium.
Renowned as an "extremist" cleric and notorious for his harsh rhetoric in support of Iran's Supreme Leader and his criticism of the opposition, Khatami has no record of political activities pre-Islamic Revolution or its early years.
In July 2013, Khatami declared that he believed that "Velayat-e-Faqih," Iran's Supreme Leader, is the regime's sole ruler, and nobody, even the elected president of Iran, could challenge him.
The Guardian Council has twelve members, elected for a six-year term. Six of them must be "fair-minded Twelver Shi'ite jurists and aware of the requirements of the time and issues of the day." They are all directly appointed by the Supreme Leader of Iran.
The other six must be "Muslim legal experts and lawyers," who are presented by the judiciary head to the Majlis Iranian parliament for approval.
One of the Guardian Council's tasks is to "verify or reject the presidential and parliamentary candidates' qualifications."