Al-Kāfi - Volume 1 > Chapter On The relationships (Nisbah) Of Allah
Hadith #4

4ـ مُحَمَّدُ بْنُ أَبِي عَبْدِ الله رَفَعَهُ عَنْ عَبْدِ الْعَزِيزِ بْنِ الْمُهْتَدِي قَالَ سَأَلْتُ الرِّضَا (عَلَيْهِ السَّلام) عَنِ التَّوْحِيدِ فَقَالَ كُلُّ مَنْ قَرَأَ قُلْ هُوَ الله أَحَدٌ وَآمَنَ بِهَا فَقَدْ عَرَفَ التَّوْحِيدَ قُلْتُ كَيْفَ يَقْرَأُهَا قَالَ كَمَا يَقْرَأُهَا النَّاسُ وَزَادَ فِيهِ كَذَلِكَ الله رَبِّي كَذَلِكَ الله رَبِّي.

4. Muhammad ibn abu ‘Abdallah in a marfu‘ manner has narrated from ’Abd al-‘Aziz ibn al-Muhtadi who has said the following. “I asked Imam Ali al-Rida (a.s.) about the Oneness of Allah.” He replied, “Whoever recites Chapter 112 of the holy Quran: In the Name of Allah, the Beneficent, the Merciful (Muhammad), say, “He is the only God (112:1). God is Absolute (112:2). He neither begets nor was He begotten (112:3). There is no one equal to Him (112:4). and also believes in it, he has really acknowledged the Oneness of Allah.” I asked, “How should I recite it (the chapter 112)?” The Imam replied, “Recite it as the people do.” And then the Imam added, “Such is Allah, my Lord. Such is Allah, my Lord.”