“I used to wish to enter the House so that I might pray inside it. The Messenger of Allah — may Allah’s peace and blessings be upon him — then took my hand and led me into the Ḥijr and said: ‘Pray in the Ḥijr if you wish to enter the House, for it is a part of the House. Your people, when they rebuilt the Kaʿbah, shortened it and excluded it from the House.’”

Narrated by Aḥmad (24616), Abū Dāwūd (2028) — and the wording is his — al-Tirmidhī (876), and al-Nasāʾī (2912), from the ḥadīth of ʿĀʾishah — may Allah be pleased with her.
Authenticated in Ṣaḥīḥ al-Jāmiʿ (3792) and Ṣaḥīḥ Abī Dāwūd (1769).

Brief Explanation of the Hadith

Among the distinguishing features of the Sacred House of Allah is the Ḥijr — the curved wall adjoining the Kaʿbah on its northern side. It is also known as al-Ḥaṭīm.
In this ḥadīth, ʿĀʾishah — may Allah be pleased with her — relates that she wished to pray inside the Kaʿbah due to its virtue, honor, and immense sanctity. The Prophet — may Allah’s peace and blessings be upon him — then took her by the hand, led her into the Ḥijr, and said: “Pray in the Ḥijr if you wish to enter the House, for it is a part of the House.” Meaning: praying therein suffices for praying inside the Kaʿbah, for it is considered a part of it in both ruling and sanctity.
It was named al-Ḥijr because it was excluded (ḥujira) from the structure of the Kaʿbah when Quraysh rebuilt it in the Jāhiliyyah. They restricted themselves to using only lawful funds for its reconstruction, and when those funds proved insufficient to complete the original foundation, they left this area outside the Kaʿbah. This is the meaning of his statement — may Allah’s peace and blessings be upon him —: “Your people, when they rebuilt the Kaʿbah, shortened it and excluded it from the House.”
It is understood from the ḥadīth that ṭawāf performed from within the Ḥijr is invalid, for in doing so the person would be circling only a portion of the House, not all of it; and ṭawāf is only valid when performed around the entirety of the House.
The ḥadīth also shows that praying inside the Kaʿbah was known to be permissible and practiced among the Companions — men and women alike — and that the Ḥijr is indeed a part of the House.