It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that he said: When Sayyidah Fatimah (may Allah be pleased with her), the mother of Sayyiduna Ali bin Abi Talib (may Allah be pleased with him), died, the Messenger of Allah (peace and blessings be upon him) took off his blessed shirt and clothed her in it, and lay down with her in her grave. Then, when he (peace and blessings be upon him) had levelled the earth over her, some people said: O Messenger of Allah! We saw you do something that you have not done with anyone. He (peace and blessings be upon him) said: "I clothed her in my shirt so that she may be dressed in the garments of Paradise, and I lay down with her in her grave so that the squeezing of the grave may be lightened for her; indeed, after Abu Talib, she was the best of Allah's creation in her kind treatment of me."
Hadith Referenceالمعجم الأوسط / باب الميم / 6935
Hadith Gradingمحدثین:فيه سعدان بن الوليد لم يُعرف، وبقية رجاله ثقات
Hadith Takhrij«قال الهيثمي: فيه سعدان بن الوليد ولم أعرفه وبقية رجاله ثقات «مجمع الزوائد ومنبع الفوائد، ج 9، ص 257»»