While we were sitting in the company of the Prophet (ﷺ) a woman came to him and presented herself (for marriage) to him. The Prophet (ﷺ) looked at her, lowering his eyes and raising them, but did not give a reply. One of his companions said, "Marry her to me O Allah's Messenger (ﷺ)!" The Prophet (ﷺ) asked (him), "Have you got anything?" He said, "I have got nothing." The Prophet (ﷺ) said, "Not even an iron ring?" He Sa`d, "Not even an iron ring, but I will tear my garment into two halves and give her one half and keep the other half." The Prophet; said, "No. Do you know some of the Qur'an (by heart)?" He said, "Yes." The Prophet (ﷺ) said, "Go, I have agreed to marry her to you with what you know of the Qur'an (as her Mahr)."
Sahih al-Bukhari Book 67, Hadith 68
← Previous Hadith (regarding His Statement): 'They ask your instruction concerning the women. Say: Allah instructs you about them ...' (4.127) It is about the female orphan who is under the guardianship of a man with whom she shares her property and he does not want to marry her and dislikes that someone else should marry her, lest he should share the property with him, so he prevents her from marrying. So Allah forbade such a guardian to do so (i.e. to prevent her from marrying).

Sahih al-Bukhari Book 67, Hadith 67 Next Hadith → that the Prophet (ﷺ) married her when she was six years old and he consummated his marriage when she was nine years old, and then she remained with him for nine years (i.e., till his death).

Sahih al-Bukhari Book 67, Hadith 69