I am the most knowledgeable of people regarding the time of this prayer. The Messenger of Allah ﷺ used to pray it when the moon set on the third night.
أنا أعلم الناس بوقت هذه الصلاة، كان رسول الله ﷺ يصليها لسقوط القمر الثالثة.
Abu Dawud (419), Tirmidhi (165), and Nasai (529) all recorded it through the route of Abu Awana, from Abu Bishr, from Bashir bin Thabit, from Habib bin Salim, from Numan bin Bashir, mentioning something similar. Its chain of transmission is sahih, except that there was disagreement over Abu Bishr, who is Jafar bin Iyas. Abu Awana narrated it as you see, and Shuba followed him, narrating from Abu Bishr in a manner similar to Abu Awana's narration.Through Shuba's route, it was narrated by Imam Ahmad (18396), Daraqutni (1/270), and Hakim (1/194), all through Yazid bin Harun from him. Its wording in the Musnad is, "I am indeed the most knowledgeable of people, or among the most knowledgeable of people, about the time the Messenger of Allah ﷺ prayed Isha. He would pray it at the point when the moon set on its third or fourth night." Daraqutni said, "Shuba was uncertain."Tirmidhi said, "Abu Awana's hadith is more sahih in our view, because Yazid bin Harun narrated from Shuba, from Abu Bishr, in a manner similar to Abu Awana's narration." End of quote.Daraqutni said, "Hushaym, Raqaba, and Sufyan bin Husayn narrated it from Abu Bishr, from Habib, from Numan, and they said 'third night,' without mentioning Bashir." End of quote.I say, through Hushaym's route it was narrated by Ibn Abu Shayba (1/330) and Hakim (1/194). Hakim said, "Raqaba bin Masqala followed him, narrating from Abu Bishr." Thus Raqaba and Hushaym agreed in narrating this hadith from Abu Bishr, from Habib bin Salim, and this is a sahih chain of transmission. Shuba and Abu Awana differed from them both, saying, "From Abu Bishr, from Bashir bin Thabit, from Habib bin Salim." End of quote.I say, as for Raqaba bin Masqala's narration, it was recorded by Nasai (528) from Jafar bin Iyas, who is Abu Bishr bin Abu Wahshiya. Abu Bishr, although he was reliable, Shuba nevertheless declared him daif regarding Habib bin Salim. As for the hadith of Sufyan bin Husayn, from Abu Bishr, from Habib bin Salim, from Numan, Daraqutni alluded to it as mentioned above.Tirmidhi, Abu Zura, and others gave preference to the narration of those who established "Bashir bin Thabit" between Abu Bishr and Habib bin Salim. Indeed, Abu Bakr bin Arabi, in Aridat Ahwazi (1/277), went so far as to declare it an error, saying, "The error of one who erred in it does not remove it from being sahih."Shuba said, "Abu Bishr did not hear from Habib bin Salim," and this is why he declared him daif in this regard, as mentioned before. By this, Tirmidhi's statement that "Abu Awana's hadith is more sahih in our view" is confirmed as sound.This hadith indicates hastening the Isha prayer after its time has come, while other hadiths indicate that it is preferable to delay it. The governing principle in this matter is what Jabir bin Abdullah mentioned, that the Prophet ﷺ would sometimes pray Isha early and sometimes late, if he saw that people had gathered he would hasten it, and if he saw that they were slow he would delay it, as mentioned before in the chapter on timing.