In conclusion, my faithful brother, if you turn over this chapter with contemplation and look at it with scrutiny after opening the locks of your heart and lifting from it the suspensions of doubt, you will see that this speech was not written except by the success of the Most Gracious. I did not gather this news except by the guidance of the King, the Bestower. If you ponder, O my brother, how we gathered for you the stray and incoming [narrations] from the books of the opponents and the Opposites (Al-Adhdad), and tied them for you with a tie to the inner meanings of the decisive Hadiths that appeared in Al-Haft Al-Sharif and the rest of the books of the People of Tawhid, the Trustworthy.
After you have known that our Masters (may their glory be magnified) are absolved from being killed, and that the killing falls upon the Opposite, the issue of joy on this day becomes a rational, logical issue that is not denied after your knowledge of the reality of the matter. Thus, the joy is in the gathering of the believing brothers, remembrance, and reviving the matter of Tawhid.
As for those who rejoice out of spite and happiness at the killing of Hussein, according to their miserable conjecture—from the Nawasib (hostiles) or the mocking atheists—they are cursed and sinful. Perhaps the Gnostic Sayyid Hashim Al-Haddad, as narrated from him in the book Al-Ruh al-Mujarrad, was pointing to this meaning regarding joy.
It is conveyed in the book Al-Ruh al-Mujarrad:
The Knower of Allah, Sayyid Hashim Al-Haddad, used to say: How heedless are these people when they grieve and hold funeral ceremonies and mourning for this slain martyr! The theater of Ashura is one of the most innovative scenes of Love (Ishq), one of the most magnificent sites of Divine Beauty and Glory, and the best manifestations of the names of Mercy and Wrath. It was for Ahl al-Bayt (peace comes from them) nothing but the crossing of degrees and ranks, the arrival at the highest peak of eternal life, the stripping away of manifestations, the realization of the Origin of the Manifest, and the absolute annihilation in the Unitary Essence. In truth, it was the day of Ahl al-Bayt's pleasure and delight, because it was the day of victory, attaining the desire, and succeeding in entering the sanctuary of Allah and the sanctuary of His safety and security. It was the day of stepping beyond partiality and entering the world of totality; the day of triumph, success and reaching the ultimate sought-after and the original goal. It is a day which, were a part of it revealed to the wayfarers, the lovers, and those enraptured on the path of Allah, it would make them amazed until the end of life from the excess of joy, and they would fall down prostrate until the Day of Resurrection in thanks to Allah."