من لا يحضره الفقيه, volume 1, page 553

Hadith.1535 - In a narration from Abdullah ibn al-Mughirah, from Imam Al-Sadiq (as), Imam (as) said: "Recite in the Salat of Ja'far (as) 'Qul Huwa Allahu Ahad' (Surah Al-Ikhlas) and ‘Qul ya-ayyuhal kaafirun’ (Surah al-Kafirun)."

Translation: Bab Ul Qaim Publications·Thaqalayn link·The Arabic above is the original.

Hadith.1536 - It is narrated from Ibrahim ibn Abi al-Bilad, who said: I asked Abu al-Hasan, meaning Imam Musa ibn Jafar Al-Kadhim (as): "What is the reward for one who prays the Salat of Ja'far?" Imam (as) said: "If they have sins equal in quantity to the sand of 'Alij and the foam of the sea, Allah (swt) would forgive them." I asked: "Is this exclusively for us?" Imam (as) said: "For whom else would it be if not for you specifically?" I then asked: "Which chapters (of the Qur'an) should be recited in it?" Imam (as) answered: "Recite 'When the Earth is Shaken with its [Final] Earthquake' (Surat al-Zalzalah), 'When the Victory of Allah (swt) has Come' (Surat al-Nasr), 'Indeed, We sent it down during the Night of Decree' (Surat al-Qadr), and 'Qul Huwa Allahu Ahad' (Surah Al-Ikhlas)."

Translation: Bab Ul Qaim Publications·Thaqalayn link·The Arabic above is the original.