The following is excerpted from al-Khatib al-Baghdadi’s biography of Imam Bukhari in Tarikh Baghdad:

Ahmad ibn al-Hasan al-Razi related that he heard Abu Ahmad ibn ‘Adi say, “I heard several shaykhs relate that Muhammad ibn Isma‘il al-Bukhari came to Baghdad and the scholars of hadith there heard about his coming. They took one hundred hadiths and changed their texts and chains of transmission, putting the text of one with the chain of another, and so on. Then they divided them between ten men, each man having ten hadiths, and told them that when the gathering began they should present them to al-Bukhari. Then they made a date with him for the gathering, which was attended by scholars of hadith from Khorasan and elsewhere as well as from Baghdad.

Once everyone at the gathering had got settled in, one of these ten men were invite to speak, and asked him about one of those hadiths. Al-Bukhari said, “I do not know it.” He kept presenting the hadiths to him one by one until he had gone through them all, and al-Bukhari kept saying, “I do not know it.” The more insightful gathering began to look at one another and say, “The man understands,” while the others suspected that al-Bukhari was inept and lacking in knowledge. Then another man of the ten was invited to speak, and asked him about one of the jumbled hadiths. He said, “I do not know it.” He asked him about another, and he said, “I do not know it.”. He kept presenting the hadiths to him one by one until he had gone through all ten, and al-Bukhari kept saying, “I do not know it.” Then the third man was invited to speak, and the fourth, until all ten had spoken and al-Bukhari had said nothing but “I do not know it.”

Then, when al-Bukhari saw they had all finished, he turned to the first man and said, “Your first hadith should have been like this, and your second should have been like this” – and so on for the third, fourth, and all the rest one after the other. He placed every text with its proper chain, and every chain with its proper text. Then he did the same with the other men, putting all their texts with their proper chains and all their chains with their proper texts. The people acknowledged his memorisation and proclaimed his excellence. When Ibn Sa‘id heard mention of Muhammad ibn Isma‘il, he would say, “There was a strong-horned ram!”

[Translated by Khalid Willams in Fath al-Bari – Victory of the Creator: Commentary on Sahih al-Bukhari – Shaykh al-Islam Ibn Hajar al-Asqalani, Visions of Reality, 1438 H/2017 CE, pp. 67-68]