Reference: Siyar A’laam an-Nubalaa – Volume 12, Page 391
Muhammad ibn Ismaa’eel al-Bukhaaree said I heard an-Najm ibn al-Fudhayl say:
[In a dream] I saw the Prophet (sal-Allaahu ‘alayhi wa sallam) [and it was] as if he was walking, and Muhammad ibn Ismaa’eel [al-Bukhaaree] was walking behind him.
[So] every time the Prophet (sal-Allaahu ‘alayhi wa sallam) raised his foot [to proceed], Muhammad ibn Ismaa’eel [al-Bukhaaree] placed his foot in the [same] place from where the Prophet (sal-Allaahu ‘alayhi wa sallam) had [just] raised his foot.