It was narrated from 'Aishah that the Messenger of Allah married her when she was six years old, and consummated the marriage with her when she was nine.
Sunan an-Nasa'i Book 26, Hadith 60
← Previous Hadith "Tell the Messenger of Allah that I am a jealous woman and that I have sons, and none of my guardians are present." He went to the Messenger of Allah and told him that. He said: "Go back to her and tell her: As for your saying that you are a jealous woman, I will pray to Allah for you to take away your jealousy. As for your saying that you have sons, your sons will be taken care of. And as for your saying that none of your guardians are present, none of your guardians, present or absent, would object to that." She said to her son: "O 'Umar, get up and perform the marriage to the Messenger of Allah," so he performed the marriage.

Sunan an-Nasa'i Book 26, Hadith 59 Next Hadith → "The Messenger of Allah married me when I was seven years old, and he consummated the marriage with me when I was nine."

Sunan an-Nasa'i Book 26, Hadith 61