He retained in his memory a mouthful of water that the Messenger of Allah ﷺ had spurted into his face from a bucket drawn from their well.
حدثنا بهز حدثني إبراهيم بن سعد حدثنا ابن شهاب
وقد كان عقل مجة مجها رسول الله ﷺ في وجهه من دلو من بئر لهم
Its isnad is sahih. This establishes that he had seen the Prophet ﷺ, contrary to what Mizzi reported, that neither his seeing him nor his hearing from him is established.The scholars have differed over the definition of a companion. Whoever says that a companion is someone who saw the Prophet ﷺ while being of an age to distinguish things and a believer would say that Mahmud was not yet of an age to distinguish things. Whoever says that mere seeing, along with belief, counts as companionship made this a proof for a child's capacity to retain and transmit knowledge.Bukhari 1/172, no. 77, Fath, Abdul-Razzaq 10/429, no. 19600, Nasai in Amal al-Yawm wal-Layla, no. 1108, and Ibn Khuzayma 3/103, no. 1709.