Question: Why did the caliphate not remain in the Prophet's Family, although its members were the most deserving?

Answer: Worldly kingdom is deceptive, and the Prophet's Family was appointed to preserve Islam's truths and the Qur'an's injunctions. In order not to be deceived by caliphate or kingdom, one should be either infallible like a Prophet or as extraordinarily pure‑hearted as the four Rightly‑Guided Caliphs, the Umayyad caliph 'Umar ibn 'Abd al‑'Aziz, or the 'Abbasid caliph al‑Mahdi. The Fatimids in Egypt, the al‑Mohads in North Africa, and the Safawids in Persia all show that worldly kingdom is not suitable for the Prophet's Family, for it causes them to neglect their essential duty of protecting and serving Islam. When they refrained from worldly kingdom, they served Islam and the Qur'an brilliantly and successfully.

Consider the leading saints descended from Hasan, particularly the four most eminent (Hasan al‑Kharaqani, Hayat ibn Qays al‑Harrani, Shaykh Hasan al‑Shadhezili, and especially 'Abd al‑Qadir al‑Jilani) and the Imams descending from Husayn, especially Zayn al‑'Abidin and Ja'far al‑Sadiq. Each became a spiritual guide of the highest rank and, dispelling the dark clouds of wrongdoing, spread the Qur'an's light and Islam's truth. They showed themselves to be true heirs of the Prophet.