Lady Zahra (as) herself made a will demanding her grave to remain hidden in order to show her disapproval and objection to those who usurped caliphate after her father.
After the demise of the Prophet Muhammad (pbuh&hf), his daughter Fatima underwent much pain and suffering. The usurpers of Caliphate raided her house in order to force her husband, Imam Ali (as), to pay allegiance to their illegal government. Meanwhile, she was beaten up and her rib was broken during the assault. As a result, she became angry with the ruling body and asked Imam Ali in her well-known will to perform her burying rites at night and insisted that he allow not the usurpers attend her funeral. After her burial, the Caliphs found their publicity at danger and tried to find out where Fatima was buried but Imam Ali (as) refused to reveal where the grave was.
The opinions of Sunni scholars about the burial place of Lady Fatima varies. Some hold the belief that she we buried in Imam Ali's house. Some of them say that she was buried in al-Baqi' cemetery referring to a narration quoted from Imam Hassan's will in which Imam Hassan (as) asked his family to bury him beside his mother.
But this seems not to be correct, because it is possible that Imam Hassan meant his grandmother, Fatima bint Asad, as it was quite common to call the grandmother 'mother'. Besides, Ibn Shaibah and Samhudi quoted a man, known as Abd al-Aziz (who was famous for his information about Medina) that Abbas, the uncle of the Prophet (pbuh&hf), was buried near Fatima bint Asad. Therefore, the grave stone located near Imam Hassan's grave in Baqi' cemetery belongs to Fatima bint Asad, the grandmother of Imam Hassan (as). Moreover, according to what is narrated from Ibn Hibban (a great 4th-century Sunni scholar and Muhaddith), Imam Hassan (as) was buried next to Fatima bint Asad.
As I mentioned earlier, Lady Zahra (as) herself wanted her grave to remain hidden in order to show the Muslim community her disapproval of those who usurped Caliphate. Lady Fatima's hidden grave is an everlasting proof of the oppression and sufferings Imam Ali (as) underwent.
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