Al-Mawardi and Ibn Khaldun have mentioned these conditions.

Al-Mawardi and Ibn Khaldun have mentioned these conditions.[^1] Infallibility; theologians have defined infallibility as: “It is a mercy Allah has given to the most perfect of His servants, and through which he (the Imam) refrains from committing crimes and offenses intentionally or unintentionally.” The Shia have unanimously agreed on that the Imam should be infallible, and that the proof of it is Hadith al-Thaqalayn in which Allah’s Apostle (a.s) has compared the Qur’an to his family.

As the Qur’an is infallible of errors and slips, and so are the Prophet’s family; otherwise the comparison and equality between them is incorrect. We have already explained that. None has such qualities except the Imams from Ahlul Bayt, who embraced Islam, protected it, led people to the good pleasure of Allah and to the obedience to Him. Al-Kumayt, the poet, has described them, saying: They are close to generosity and far from the injustice in the ties of the precepts.

They give right answer to the matter over which people differ. They have established the rules of Islam. They are sufficient protectors at war when it becomes hot. They are like rain when the people suffer from drought. They are like a shelter for the nursemaid of orphans. [^1] Al-Ahkam al-Sultaniya, p. 4. Al-Muqaddama, p. 135. They are overweighing in opinion, having perfect justice in behavior, and knowledgeable of heavy affairs.

They are leaders, but they are not like those who rule people and sheep in the same way.[^1] Most surely the Imams from the Ahlul Bayt, peace be on them, have displayed their infallibility of errors and slips through their behavior and guidance. The events have proved that and indicated that they are unique in the history of mankind, for they had great merits, fear of Allah, and commitment to the religion.

His Appointment The Shia have believed that the community and the influential have no right to appoint the Imam. They have also believed that electing the Imam is invalid and choosing him is impossible. Therefore, Imamate is similar to prophethood. As man has no right to find and form prophethood, he has no right in finding and forming the Imamate. That is because none knows the infallibility, which is among the qualities of the Imam, except Allah, Who knows the things hidden in souls.

This has been explained and indicated by Imam al-Mehdi (a.s) through his talk with Sa’d bin Abdullah, who asked him about the reason for preventing men from electing an Imam over them.