The Book of Pilgrimage (Kitab Al-Hajj)
Muslim :: Book 7 : Hadith 3091
Ibn Abbas reported that Allah's Apostle (may peace be upon him) met some riders at al-Rauha and asked who they were. They replied that they were Muslims. They said: Who art thou? He said: (I am) Messengef of Allah. A woman (then) lifted up a boy to him and said: Would this child be credited with having performed the Hajj? Thereupon he said: Yes, and you will have a reward.