This could be true because just after Mu’ammal bin Isma’eel, in at-Tarikh al-Kabeer, Imam Bukhari listed Mu’ammal bin Sa’eed and declared him Munkar al-Hadith. It may be that some scholar mistakenly took it for Mu’ammal bin Isma’eel.
However, on the other hand it also seems difficult because more than one scholars had attributed this to Bukhari, some have attributed the statement “Munkar al-Hadith” while some have attributed mere weakening without specifying any term. This includes the likes of Imam al-Mizzi, al-Dhahabi, al-Haythami, Ibn Hajar al-Asqalani and al-Buqa’i. It is necessary, before reaching to a conclusion, that different manuscript of Tarikh Kabeer and other books on Rijal by al-Bukhari should be analyzed carefully. WAllahu A’alam.
With regards to the claim of Shaykh Zai that Imam Bukhari has included his narrations in his “Saheeh” in support and hence he was Thiqah, this is again a false analogy.
Imam Bukhari intentionally avoiding Mu’ammal and not taking him as hujjah, indicates that there was some reason for which he avoided him. Similarly Imam Muslim completely avoided him. Hafiz Abu Umar Ibn As-Salah said in his famous Muqaddimah on ‘ilmul hadeeth (pg.84), “Know that the narrations of those who is not Hujjah (as a narrator) and rather he is among weak narrators, is sometimes cited in case of Mutabi’ah and Shawahid. And in the book of Bukhari and Muslim there are several weak narrators cited as Mutabi’ah and Shawahid.”
Inclusion of some weak narrators in Ta’aaleeq of Saheeh is a fact which cannot be denied. The following are narrators in Ta’aleeq of Saheeh:
1. Ibrahim bin Isma’eel bin Mujamma’: Imam Bukhari said, “he was the person with a lot of doubts (Kathir al-Wahm)”.
2. Huraith bin Abi Matar: Bukhari said, “feehi nazr”.
3. Ubaidulla bin Sa’eed bin Muslim al-Ju’fi, Abu Muslim: Bukhari said,”feehi nazar”.
4. Umar Abu Salamah bin Abdur-Rahman: Bukhari said,”Sadooq, except that he was opposed (by scholars) in some of narrations”.
5. Imran bin Dawar: Bukhari, “truthful, he used to fall in doubts (yahim)”.
6. Mu’awiyah bin Abdul Kareem: Ibn Abi Hatim said, “Bukhari listed him amongst weak narrators”.
7. Yahya al-Kindi: Bukhari said, “He was not known and no one back (support) him (lam Yutaba’ alaih)”.
One can refer to entries of these narrators in Tahdheeb at-Tahdheeb by Ibn Hajar.
Sh Zubair quoted from Muhammad bin Tahir al-Maqdisi that he said regarding a narrator, “In fact He (Bukhari) has taken narrations from him in many places as Istish-haad to indicate that he is Thiqah”, and then he (Sh Zai) himself concluded, “This proves that Mu’ammal is Thiqah according to Imam Bukhari, not Munkir ul-Hadeeth”.
I say: The statement of al-Maqdisi is regarding some narrators of Sahihayn who were well famous scholars but still Shaykhain avoided them, except in Mutabi’ah or Shawahid. This doesn’t mean for every single narrators mentioned by Shaykhain in support or for back up. Even if we accept that al-Maqdisi meant it for every single narrator, then also there is no reason to blindly follow him and leave the facts described above. Therefore, I could not understand the basis for the statement of Shaykh Zubair Ali Zai that Mu’ammal was Thiqah according to Imam Bukhari.
In conclusion, Imam Bukhari only mentioned Mu’ammal in Ta’aleeq, not in the main Ahadeeth of Sahih Bukhari. WAllahu A’alam.