al-Bukhaari did not narrate anything directly from the Prophet

, rather he narrated from trustworthy shaykhs, who attained the highest degree of memorization, precision and trustworthiness, who in turn had narrated from equally reliable shaykhs, all the way back to the Sahaabah who narrated from the Messenger of Allaah

. The smallest number of narrators between al-Bukhaari and the Prophet

is three. So we rely upon Saheeh al-Bukhaari because he chose the narrators from whom he transmitted hadeeth with the utmost care, and they are the most trustworthy. Moreover, he would not write down any hadeeth in his Saheeh until he had done ghusl, then prayed two rak’ahs and prayed istikhaarah, asking Allaah to guide him with regard to writing down this hadeeth; then he would write it down. It took him sixteen years to write this book, which the ummah accepted and unanimously agreed that what is narrated in it is saheeh; and Allaah has protected this ummah from agreeing upon misguidance.
Imam al-Nawawi (may Allaah have mercy on him) said in his introduction to Sharh Muslim (1/14): “The scholars (may Allaah have mercy on them) are agreed that the most sound of books after the Qur’aan are the two Saheehs of al-Bukhaari and Muslim, which were accepted by the ummah. The book of al-Bukhaari is the more sound and the more beneficial of the two.”