Unlike religious leaders of Christianity, Ayatollah is entitled to deal with political matters and even to head the State but only if he can do it properly (ii)- If Ayatollah fails on Fakhirzadeh matter then Iran should adopt secularism.  

The US prominent media is reporting that - “One American official — along with two other intelligence officials — said that Israel was behind the attack on the scientist” (https://www.nytimes.com/2020/11/27/world/middleeast/iran-nuclear-scientist-assassinated-mohsen-fakhrizadeh.html ). Scientist Mohsen Fakhirzadeh (supposed to be working on nuclear program for peaceful purposes, as claimed by Iran) was killed in a terrorist attack on November 27 near Iran’s capital Tehran about which prominent media of India also reported that - “One US official — along with two other intelligence officials — said Israel was behind the attack on the scientist. It was unclear how much the United States may have known about the operation in advance” (https://timesofindia.indiatimes.com/world/middle-east/irans-top-nuclear-scientist-killed-in-attack-state-media-say/articleshow/79455899.cms).

The killings of Fakhirzadeh and his guards etc have created huge problems for Ayatollah Khomenei the ‘Supreme Leader of Iran’.  The Sunnis are about 88 % of Muslim population whereas Shias are only about 12%. Iran is the only major country where Shias are in the overwhelming majority and which is ruled (after 1979 revolution) by religious leader Ayatollah Seyyed Ali Khomenei . Hence the Shias all over the world accept the leadership of Ayatollah in religious (rather ‘Deeni’) matters. The Muslims do not consider Islam as merely a religion but a ‘Deen’ (which deals with every aspect of life including politics) hence for the Shia-Muslims what Ayatollah does / says is a matter of utmost importance for them.

The West led by the USA thinks that the 5 permanent members of the UN and Israel, Pakistan, India have some divine right to have nukes but others (Iran, North Korea etc do not have this). Despite de-nuclearization & non-proliferation regime of UN / IAEA the nukes of said privileged club have not been eliminated. On the issue of nuclear proliferation the West led by the USA has harassed Iran immensely but so far Iran has not succumbed hence the reputation and credibility of Ayatollah have not taken a hard hit but the killing of  Fakhirzadeh etc is a different matter which President of Iran Hassan Rouhani has termed as terrorist act but Rouhani has also said that Iran would retaliate over Mohsen Fakhirzadeh's killing at a time of its choosing. 

Ayatollah should not accept this improper & cowardly approach of Rouhani and instead should get UNSC moved against this alleged State terrorism. Moreover Iran should not wait for Biden to come in White House (if Trump loses electoral fraud cases in the US Supreme  Court) to sort out the matters with Iran about the nuclear deal. Ayatollah should understand that nuclear deal and State terrorism are different matters and need to be handled differently if rule-of-law is to be ensured which is the only way to bring peace, justice and prosperity to any country.

Now when US officials have openly said that Israel is behind this killing of Fakhirzadeh etc then Iran is supposed to immediately move the United Nations to call the urgent session of  its Security Council (UNSC)  to ask the USA to furnish the evidence to the UNSC (on the basis of which the US-officials accused that Israel is responsible for this killing of Fakhirzadeh etc) and then UNSC to ask Israel to give the reply in its defense.

“[At the same time Iran should know that it will not be able to get desired results from UNSC in  Fakhirzadeh matter unless Iran mends its policies towards terrorism it spreads in NAME region where Shia militants supported by Iran spills blood in Sunni majority countries like Syria, Yemen etc. Hence Iran simultaneously should declare that it will cooperate with world community in bringing peace to NAME region through democracy which requires only free & fair elections in these countries (but not through illegitimate ballots like postal ballots which are also susceptible to electoral frauds which, as per Republicans, has happened in the US - 2020 elections ]”

The further course of action for Iran at UNSC would depend on whether Israel can provide a proper & satisfactory explanation or fails to do it. But if Ayatollah fails to move the world community (through UN) to bring Israel to justice even in such an open and shut case (as alleged by US-officials) then Ayatollah should give-up politics and also the office of the  ‘Supreme Leader of Iran’ and instead should confine to only religious matters as Christian religious leaders do in Christian majority countries under secular constitution.