Sunan Ibn Majah, Chapter: The Chapters on Medicine

"I saw the Messenger of Allah (saw) stoning the 'Aqabah Pillar from the bottom of the valley on the Day of Sacrifice, then he went away. A woman from Khath'am followed him, and with her was a son of hers who had been afflicted, he could not speak. She said: 'O Messenger of Allah! This is my son, and he is all I have left of my family. He has been afflicted and cannot speak.' The Messenger of Allah (saw) said: 'Bring me some water.' So it was brought, and he washed his hands and rinsed out his mouth. Then he gave it to her and said: 'Give him some to drink, and pour some over him, and seek Allah's healing for him.'" She (Umm Jundub) said: "I met that woman and said: 'Why don't you give me some?' She said: 'It is only for the sick one.' I met that woman one year later and asked her about the boy. She said: 'He recovered and became (very) smart, not like the rest of the people.'"