It is transmitted in a report attributed to Ubayy ibn Kaʿb, who reports from the Prophet: ‘One who recites Sūrat al-Muzzammil will have difficulty and distress lifted from him in this world and the hereafter.’‎‎^{‎‎‎[1]Tabrisi, 10/565; Tabrisi.J, 4/381.}

A report attributed to Manṣūr ibn Ḥāzim transmits Imam al-Ṣādiq (a) as saying: ‘One who recites Sūrat al-Muzzammil at night or at the end of the night will have both the day and the night, along with the surah, as witnesses [in his favour]. And God will grant him a pure life and a pure death.’^{‎‎‎[2]Tabrisi, 10/565; Tabrisi.J, 4/381; Burhan, 5/515; Thawab, p. 120.}

It is reported from the Prophet who said: ‘One who recites this surah will have a reward due to one who has manumitted slaves for the sake of God equal to the number of the jinn and devils. God will remove difficulty from him in this world and the hereafter. And the one who persists in the recitation of this surah will see the Prophet in his dream and may ask from him what his heart desires.’‎‎^{‎‎‎[3]Burhan, 5/515.}

The Prophet is reported to have said: ‘One who persists in the recitation of this surah will have difficulties removed from him by God and will see the Prophet in his dream.’‎‎^{‎‎‎[4]Burhan, 5/515.}

Imam al-Ṣādiq (a) is attributed to have said: ‘Whoever persists in the recitation of this surah and sees the Prophet and asks him for what he wants, God will grant him whatever he wants of goodness. And the one who recites it on Friday night a hundred times will have God forgive him a hundred sins and have a hundred good deeds registered to his credit, the kind which qualifies ten good deeds in lieu of each, as God has said [in the Quran].’‎‎^{‎‎‎[5]Burhan, 5/515.}

However, it needs to be cautioned here that these merits are obtained when recitation is necessarily accompanied with acting on the contents of the surah, i.e. the acts of getting up at night, establishing prayers, recitation of the Quran, repentance, payment of zakat, and giving in charity. These benefits would not accrue with mere recitation that is devoid of action.‎‎^{‎‎‎[6]Amthal, 19/125.}

[1] Tabrisi, 10/565; Tabrisi.J, 4/381.
[2] Tabrisi, 10/565; Tabrisi.J, 4/381; Burhan, 5/515; Thawab, p. 120.
[3] Burhan, 5/515.
[4] Burhan, 5/515.
[5] Burhan, 5/515.
[6] Amthal, 19/125.