From al-Asbagh ibn Nubata, from the Commander of the Faithful Ali ibn Abi Talib (AS), who said: A supererogatory prayer in this mosque equals a lesser pilgrimage with the Prophet (PBUH), and an obligatory prayer equals a hajj with the Prophet (PBUH); and a thousand prophets and a thousand successors have prayed in it. (al-Mazar al-Kabir, vol. 1, p. 123)
The Commander of the Faithful (AS) said concerning the mosque of Kufa: A supererogatory prayer in it is equal to a lesser pilgrimage, and an obligatory prayer is equal to a hajj performed in the company of the Prophet (PBUH). Then he said: Many prophets and successors of prophets have prayed in the mosque of Kufa.
And by the same chain, from Salih, from al-Harith ibn al-Mughira, from Abu Abd Allah (AS), who said: God has angels appointed over the grave of Husayn (AS); when a man resolves to visit him, they surround him and sanctify him, and the Commander of the Faithful (AS) calls out to them: I am the guarantor that your needs will be fulfilled and that affliction will be turned away from you in this world and the next. (al-Mazar al-Kabir, vol. 1, p. 329)
Imam Sadiq (AS) said: There are angels appointed over the grave of Husayn ibn Ali (AS) to take the visitors under the shelter of their protection and to sanctify them; and the Commander of the Faithful (AS) addresses the visitors of Husayn (AS) and says: I am the guarantor that your needs will be fulfilled and that the afflictions of this world and the next will be turned away from you!