The Night Prayer
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 71
وَ رُوِيَ: «أَنَّ مَنْ قَرَأَ فِي اَلرَّكْعَتَيْنِ اَلْأَوَّلَتَيْنِ مِنْ صَلاَةِ اَللَّيْلِ فِي كُلِّ رَكْعَةٍ مِنْهُمَا اَلْحَمْدَ مَرَّةً وَ «قُلْ هُوَ اَللّٰهُ أَحَدٌ» ثَلاَثِينَ مَرَّةً اِنْفَتَلَ وَ لَيْسَ بَيْنَهُ وَ بَيْنَ اَللَّهِ عَزَّ وَ جَلَّ ذَنْبٌ إِلاَّ غَفَرَ لَهُ.
It is narrated: "Whoever recites Surah Al-Fatiha once and 'Qul Huwa Allahu Ahad' (Surah Al-Ikhlas) thirty times in each of the first two Rak'ahs of the night prayer, he will finish his prayer without any sin remaining between him and Allah سبحانه وتعالى, the Mighty and Glorious, except that He forgives it”.
- Ṣaḥīḥ al-Faqīh