عن إبن عباس قال لما ماتت فاطمة أم علي بن ابي طالب خلع رسول الله ﷺ قميصه وألبسها إياه وإضطجع معها في قبرها فلما سوّى عليها التراب قال بعضهم يا رسول الله رأيناك صنعت شيئاً لم تصنعه بأحد فقال إني ألبستها قميصي لتلبس من ثياب الجنة وإضطجعت معها في قبرها ليُخفَّف عنها من ضغطة القبر
المعجم الأوسط للطبراني باب من إسمه محمد ٦٩٣٥
From Ibn ‘Abbas, who said: When Fatimah the mother of ‘Ali ibn Abi Talib died, the Messenger of Allah (SAW) took off his gown and clothed her with it, then laid down with her in her grave. And when the earth had just covered her, some of the people said: Oh Messenger of Allah, we have seen you do something that you haven’t done to anyone before. He said: Indeed I clothed her with my gown so she would be clothed with the garments of Jannah, and I laid down with her in her grave to lighten the burden of the grave on her.
Al-Tabarani, Al-mu’jam Al-awsat [The Intermediate Lexicon], Section: narrations from those named Muhammad (number 6935)