Is visitation (ziyarah) of Imam Hussain (p) firmly established as an authentic [religious] practice?
It is narrated that Imam al-Baqir (p) said: “al-Hussain son of Ali (p) asked the Prophet (pbuh), “Oh Father what is the reward for one who visits you?” The Prophet (pbuh) replied “he who visits me, your father, your brother (i.e. al-Hassan (p)), or you, becomes deserving of my visiting him on the day of resurrection such that I rid him of his sins.
It was also narrated by Imam al-Sadiq (p): “Whoever visits the grave of al-Hussain (p) and is aware of his right shall be given the status of the higher ones (illiyeen).” He also said “whoever visits one of us [the Imams] is like one who visited al-Hussain (p).”