Praise be to Allaah.  

Ibn Hazam said: 

It is permissible for one who has done tayammum to lead in prayer people who have done wudoo’, for one who has done wudoo’ to lead people who have done tayammum, for one who has wiped over his socks to lead those who have washed their feet and for one who has washed his feet to lead people who have wiped over their socks, because each of those whom we have mentioned has done what he is obliged to do. None of them is more taahir (pure) than another, and none of them is more complete in prayer than another. The Messenger of Allaah (peace and blessings of Allaah be upon him) enjoined that when the time for prayer comes, the one who has most knowledge of the Qur’aan should lead them in prayer; he (peace and blessings of Allaah be upon him) did not specify anything other than that. If there had been any obligation other than that which he mentioned, he would have explained it and would not have neglected it – Allaah forbid. This is the view of Abu Haneefah, Abu Yoosuf, Zafar, Sufyaan, al-Shaafa’i, Dawood, Ahmad, Ishaaq and Abu Thawr. That was narrated from Ibn ‘Abbaas, ‘Ammaar ibn Yaasir and a group of the Sahaabah (may Allaah be pleased with them). It is also the view of Sa’eed ibn al-Musayyib, al-Hasan, ‘Ataa’, al-Zuhri and Hammaad ibn Abi Sulaymaan. 

It was narrated that ‘Ali ibn Abi Taalib disallowed that, and said that one who has done tayammum should not lead in prayer people who have done wudoo’, and one whose wudoo’ is valid for a limited period should not lead those whose wudoo’ is valid indefinitely. Al-Rabee’ah said: one who has done tayammum because of janaabah (impurity because of sexual activity) should not lead anyone in prayer except others who are in the same state. This was also the view of Yahyaa ibn Sa’eed al-Ansaari. 

Muhammad ibn al-Hasan and al-Hasan ibn Hayy said: he should not lead them in prayer. 

Maalik and ‘Ubayd-Allaah ibn al-Hasan said that he should not lead them in prayer, but if he does then the prayer is valid. 

Al-Oozaa’i said: he should not lead them in prayer unless he is an ameer (leader). 

‘Ali – i.e., Ibn Hazm – said: there is no evidence for disallowing that or regarding it as makrooh, either from the Qur’aan or the Sunnah or from scholarly consensus (ijmaa’) or from analogy (qiyaas); the same applies to categorizing people in that manner. And Allaah is the Source of strength.