From Sahih Muslim (Hadith 3253):
Ibn Abbas reported that Allah's Apostle (ﷺ) 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
Reference: Muslim 3253