It was Khadījah.
Gabriel asked, “Who is this, O Muḥammad?”
He replied,
“This is the truthful woman of my community.”
Gabriel said, “I have come to her with a message from the Lord—Glorified and Exalted—conveying His greeting of peace and giving her the glad tidings of a house in Paradise made of qasab, far removed from any flame, wherein there is neither weariness nor clamor.”
She responded, “Allah is Peace, and from Him comes peace. Peace, mercy, and blessings of Allah be upon you both, O Messenger of Allah. What is this house that is made of qasab?”
He said, “It is a hollow pearl set between the house of Mary daughter of ʿImrān and the house of Āsiyah daughter of Muzāḥim; both of them will be among my wives on the Day of Resurrection.”
The narration affirming that Allah sent greetings to Khadījah and promised her a house in Paradise made of qasab, in which there is no clamor and no fatigue, is established in the Ṣaḥīḥ (1); however, this particular wording with its additional details is very unusual, and all of these reports warrant scrutiny in their chains of transmission.
Ibn ʿAsākir also related, through Abū Zurʿah al-Dimashqī: ʿAbd Allāh ibn Ṣāliḥ reported to us, saying: Muʿāwiyah narrated to me, from Ṣafwān ibn ʿAmr, from Khālid ibn Maʿdān, from Kaʿb al-Aḥbār, that Muʿāwiyah asked him about the Rock—meaning the Rock of Bayt al-Maqdis.
He replied, “The Rock rests upon a palm-tree, the palm-tree stands over a river of the rivers of Paradise, and beneath the palm-tree Mary daughter of ʿImrān and Āsiyah daughter of Muzāḥim are stringing the necklaces of the people of Paradise until the Hour is established.”
He then transmitted it through the route of Ismāʿīl ibn ʿAyyāsh (2), from Thaʿlabah ibn Muslim, from Masʿūd ibn ʿAbd al-Raḥmān, from Khālid ibn Maʿdān, from ʿUbādah ibn al-Ṣāmit, from the Prophet (peace and blessings be upon him) in similar wording. This narration is objectionable via that chain; in fact, it is fabricated. Abū Zurʿah likewise reported it from ʿAbd Allāh ibn Ṣāliḥ, from Muʿāwiyah, from Masʿūd ibn ʿAbd al-Raḥmān, from Ibn ʿĀbid, that Muʿāwiyah asked Kaʿb about the Rock of Bayt al-Maqdis, and he mentioned the same.
Al-Ḥāfiẓ Ibn ʿAsākir said, “Its being the statement of Kaʿb al-Aḥbār is more plausible.”
I say: Kaʿb al-Aḥbār derived such remarks from the Isrāʾīliyyāt, some of which are fabricated inventions contrived by their heretics or their uninformed, and this is one of them. Allah knows best.