Abu Ahmad ibn Adi al-Jurjani: People acknowledged his memorization and submitted to his virtue.
Abu al-Hasan al-Khazraji: The Hafiz, Commander of the Faithful in the Hadith of the Master of the Messengers.
Abu Bakr ibn Abi Shaybah: We have not seen anyone like Muhammad ibn Ismail.
Abu Ja'far al-Musnadi: Muhammad ibn Ismail is an Imam, and whoever does not consider him an Imam has accused him.
Abu Hatim ibn Hibban al-Busti: He was one of the best of people who collected, compiled, travelled, memorized, and narrated Hadith. He was known for his great care for narrations, his memorization of traditions, his knowledge of history, his awareness of people's lives, his adherence to hidden piety, and his constant worship until he died, may Allah have mercy on him.
Abu Abd Allah al-Hakim al-Naysaburi: The Imam of the people of Hadith
Abu Isa al-Tirmidhi: I have not seen anyone in Iraq or Khorasan more knowledgeable than Muhammad ibn Ismail in the meanings of defects, history, and knowledge of chains of narration.
Abu Mus'ab al-Zuhri: Muhammad ibn Ismail is more knowledgeable in Fiqh and more insightful than Ibn Hanbal, in our view. And once he said: If I had met Malik and looked at his face and the face of Muhammad ibn Ismail, I would have said both are one in Fiqh and Hadith.
Ahmad ibn Hanbal: Memorization has reached its peak with four people from Khorasan: Abu Zur'ah al-Razi, Muhammad ibn Ismail al-Bukhari, Abdullah ibn Abd al-Rahman al-Samarqandi, and al-Hasan ibn Shuja' al-Balkhi. And once he said: Khorasan has not produced anyone like Muhammad ibn Ismail.
Ahmad ibn Siyar al-Marwazi: He travelled extensively for Hadith, excelled in it, and was insightful. He had good knowledge and good memorization, and he used to practice Fiqh.
Ahmad ibn Shu'ayb al-Nasa'i: Trustworthy, reliable, a man of Hadith, intelligent.
Ahmad ibn Nasr al-Khaffaf: The pious, pure scholar, whom I have not seen anyone like, is Muhammad ibn Ismail. He is more knowledgeable in Hadith than Ishaq, Ahmad, and others by twenty degrees. Whoever says anything against him, upon him be a thousand curses from me.
Ishaq ibn Rahawayh: O people of Hadith, look at this young man and write from him, for if he had been in the time of al-Hasan al-Basri, people would have needed him for his knowledge of Hadith and his Fiqh.
Ismail ibn Abi Uways: Whenever al-Bukhari selected from his book, Ismail would copy those Hadiths for himself and say: 'These are Hadiths that Muhammad ibn Ismail selected from my narration.'
Ibn Hajar al-'Asqalani: The Mountain of Preservation and the Imam of the World in the Fiqh of Hadith.
Al-Husayn ibn Muhammad al-Ji'ani: I have not seen anyone like Muhammad ibn Ismail. Muslim al-Hafiz could not reach the level of Muhammad ibn Ismail. I saw Abu Zur'ah and Abu Hatim listening attentively to Muhammad ibn Ismail. And once he said: Muhammad ibn Ismail was a nation among nations. He was more knowledgeable than Muhammad ibn Yahya in such and such. Muhammad ibn Ismail was religious, virtuous, and good at everything.
Al-Khatib al-Baghdadi: The Imam in the science of Hadith.
Al-Dhahabi: The Imam, author of al-Sahih. He was a leading Imam, Hafiz, authority, a head in Fiqh and Hadith, a Mujtahid, and one of the unique scholars, with piety and righteousness.
Al-Mizzi: The Hafiz, author of al-Sahih, the Imam of this matter, the one to be followed in it, and the one whose book is relied upon among the people of Islam.
Rajab ibn Murji al-Ghaffari: The superiority of Muhammad ibn Ismail over scholars is like the superiority of men over women. He is a sign from the signs of Allah walking on the face of the earth.
Salih ibn Muhammad Juzra: When asked about Muhammad ibn Ismail, Abu Zur'ah, and Abdullah ibn Abd al-Rahman, who was the most knowledgeable in Hadith, he said: Muhammad ibn Ismail and Abu Zur'ah are the most memorizing and have the most Hadith. And once he said: I have not seen anyone from Khorasan more understanding than him.
Abdullah ibn Abd al-Rahman al-Darimi: I have seen the scholars in the Two Holy Mosques, Hijaz, Sham, and the two Iraqs, but I have not seen anyone more comprehensive than Abu Abdullah Muhammad ibn Ismail al-Bukhari.
Abdan ibn Ahmad al-Ahwazi: I have not seen with my own eyes a young man more insightful than this and he pointed to Muhammad ibn Ismail.
Ali ibn al-Madini: When he narrated Hadith, people turned to him as if they were in awe of him. And once he said: He has not seen anyone like himself.
Ali ibn Hajar al-Sa'di: Khorasan produced three: Abu Zur'ah al-Razi in Ray, Muhammad ibn Ismail al-Bukhari in Bukhara, and Abdullah ibn Abd al-Rahman in Samarkand. Muhammad ibn Ismail, in my view, is the most insightful, knowledgeable, and understanding of them.
Amr ibn Zurarah: Do not hide anything from Abu Abdullah, for he is more knowledgeable, learned, and insightful than us.
Amr ibn Ali al-Fallas: A Hadith that Muhammad ibn Ismail does not know is not a Hadith.
Fadlak al-Razi: He was asked about Abu Zur'ah and Muhammad ibn Ismail, who is more memorizing? He said: I had not met Muhammad ibn Ismail before, so I met him between Hulwan and Baghdad. He said: I went back with him for a stage. He said: I tried my best to bring a Hadith that he did not know, but I could not. He said: And I am more familiar with Abu Zur'ah than the number of his hair.
Qutaybah ibn Sa'id: The youth of Khorasan are four: Muhammad ibn Ismail, Abdullah ibn Abd al-Rahman, Zakariya ibn Yahya al-Lului, and al-Hasan ibn Shuja' al-Balkhi.
Muhammad ibn Ishaq ibn Khuzaymah: I have not seen under the sky anyone more knowledgeable in the Hadith of the Messenger of Allah (peace and blessings of Allah be upon him) nor more memorizing of it than al-Bukhari.
Muhammad ibn Bashshar Bundar: The memorizers of the world are four: Abu Zur'ah in Ray, Muslim ibn al-Hajjaj in Nishapur, Abdullah ibn Abd al-Rahman al-Darimi in Samarkand, and Muhammad ibn Ismail al-Bukhari in Bukhara. And once he said: Abdullah ibn Abd al-Rahman al-Samarqandi, Muhammad ibn Ismail al-Bukhari, and Abu Zur'ah Ubayd Allah ibn Abd al-Karim al-Razi are my students who came out of my teaching.
Muhammad ibn Rafi' al-Naysaburi: Do not hide anything from Abu Abdullah, for he is more knowledgeable, learned, and insightful than us.
Muhammad ibn Salam al-Jumahi: He said to Muhammad ibn Ismail: Look into my books, and whatever you find wrong in them, mark it so that I do not narrate it. Muhammad ibn Salam used to write next to the Hadiths that Muhammad ibn Ismail considered sound: 'The boy is pleased.' And next to the weak Hadiths, he would write: 'The boy is not pleased.' So one of his companions said to him: Who is this boy? He said: The one who has no equal, Muhammad ibn Ismail.
Muhammad ibn Abd Allah ibn Numayr: We have not seen anyone like him.
Muhammad ibn Yahya al-Dhuhali: He advised listening to him when he arrived in Nishapur.
Muslim ibn al-Hajjaj al-Naysaburi: Only an envious person would hate him, and I bear witness that there is no one like him in the world. And once he said: The teacher of teachers, the master of Hadith scholars, and the physician of Hadith in its defects.
Maslamah ibn al-Qasim al-Andalusi: Trustworthy, highly respected, knowledgeable in Hadith.
Na'im ibn Hammad: The Faqih of this Ummah.
Yahya ibn Ja'far al-Baykandi: If I could increase the lifespan of Muhammad ibn Ismail, I would have done it. My death will be the death of one man, but the death of Muhammad ibn Ismail is the loss of knowledge.
Yahya ibn Muhammad ibn Sa'id: The butting ram.
Ya'qub ibn Ibrahim al-Dawraqi: The Faqih of this Ummah.