Bukhari

Hadith Commentary:
The word "maftoon" has been translated as "rebel," meaning one who turns away from the command of the true and rightful Imam.
And by "innovator" (mubtadi‘), what is meant is a general innovator.
Whether his innovation (bid‘ah) is doctrinal, such as that of the Shi‘a, Khawarij, Murji’ah, Mu‘tazilah, etc., or practical, such as one who ties the sehra (wedding garland), performs the third-day or tenth-day rituals (tija, daswan), participates in ta‘ziyah or carries the ‘alam (standard), lights lamps on graves, holds gatherings for mawlid (the Prophet’s birthday), music, or elegy (marsiya)—provided that their innovation does not reach the level of disbelief (kufr) or polytheism (shirk).
If it reaches the level of disbelief or polytheism, then prayer behind them is not valid.
It is stated in Tashil that "Sunnah" refers to hadith, and "Jama‘ah" refers to the Companions (Sahabah) and Followers (Tabi‘in). Those who follow the noble hadith and, in belief and practice, are upon the way of the Companions and Followers—these alone are Ahl al-Sunnah wa’l-Jama‘ah; all others are innovators (mubtadi‘).
(Maulana Waheed al-Zaman)

Hadith Commentary:
(1)
When Uthman (radi Allahu anhu) was under siege, in his absence, Abu Umamah Sahl bin Hunayf, Abu Ayyub al-Ansari, and Talhah bin Ubaydullah (radi Allahu anhum) led some prayers. Ali (radi Allahu anhu) performed the duty of leading the Eid al-Adha prayer, but the "imam of fitnah" refers to Kinanah bin Bishr. Although some have written that it was Abdur Rahman bin Udays, who was the leader of the Egyptian rebels, this is not correct. According to Imam Bukhari (rahimahullah), it is valid to pray behind a sower of discord (fitnah-monger), because according to the aforementioned narration, Uthman (radi Allahu anhu) instructed to perform prayer behind the imam of fitnah. In one narration, it is mentioned that the people of Madinah disliked praying behind the besiegers in the Prophet’s Mosque, but Uthman al-Ghani (radi Allahu anhu) held the position that whoever calls you to prayer, you should respond to him. From this narration, it is also understood that especially in times of tribulation (fitnah), one should be diligent in performing prayer in congregation (jama‘ah), so that the congregation does not fall into further division. And it is better to pray behind a disliked person than to abandon the congregational prayer. (Fath al-Bari: 2/245) Imam Malik (rahimahullah) held a very strict position regarding prayers during times of tribulation, and in such circumstances, he advocated performing all prayers at home. Imam Bukhari (rahimahullah), by establishing this chapter heading, has proven its permissibility and supported the majority (jumhur).
(2)
There are two types of mukhannath (effeminate men):
*Congenital: Those who naturally possess feminine mannerisms. In this case, there is no blame.
*Affected: Those who deliberately and artificially imitate the actions of women. These people are blameworthy.
In case of necessity, there is no harm in praying behind them, provided that not praying would lead to tribulation (fitnah). In ordinary circumstances of choice, one should not pray behind them. (Fath al-Bari: 2/246)