Imām Ja'far ibn Muhammad al-Sādiq (alayhi salām) said:
"Recite Sura al Fajr in your obligatory (wājib) and supererogatory (Nāfilah) morning Prayers, for it is particularly related to Imām Husayn (alayhi salām). Have you not heard the words of Allāh the Exalted in this Verse (Ayāh):
O Tranquilled Soul at (complete) rest! Return to your Lord, well-pleased (with Him), (and) His being well-pleased with you.” (Surah al-Fajr, 89:27-30).
Here Imām Husayn (alayhi salām) is referred to as the "Tranquilled Soul, well-pleased (with Allāh) and His being well-pleased with him.”
His companions from the family of the Prophet, are those who will be pleased with Allāh on the day of Qiyāmah and Allāh too will be pleased with them. Verily this Sura is particularly connected to Imām Husayn, his followers (Shi'āh), and the followers (Shi'āh) of the Progeny of Prophet Muhammad (salla llāhu ʿalayhi wa-alehe wa-sallam). The one who continuously recites this Sura will remain with Imām Husayn (alayhi salām) in Paradise in his elevated station, and verily Allāh is Predominant and All-Wise."
[Reference: Nafasul Mahmum, Section 2, Hadith 21]
(السلام عليک يا ابا عبد الله الحسين (ع