Imam Reza (a.s.) informed Rayyaan b. Shabeeb about cursing Imam Husain’s (a.s.) killers – ‘…O Ibne Shabeeb! If you would like to accompany the Prophet (s.a.w.a.) in the chambers of Paradise, then curse the murderers of Husain…’ Oyoon Akhbaar al-Reza (a.s.) chap 28 trad 53