Al-Kāfi
Hadith 17383ـ عَلِيُّ بْنُ إِبْرَاهِيمَ عَنْ أَبِيهِ عَنِ ابْنِ أَبِي عُمَيْرٍ عَنِ ابْنِ أُذَيْنَةَ عَنِ الْفُضَيْلِ بْنِ يَسَارٍ وَالْفَضْلِ بْنِ عَبْدِ الْمَلِكِ وَبُكَيْرٍ قَالُوا سَمِعْنَا أَبَا عَبْدِ الله (عَلَيْهِ الْسَّلام) يَقُولُ كَانَ رَسُولُ الله (صلّى اللهُ عَلَيْهِ وَآلِه) يُصَلِّي مِنَ التَّطَوُّعِ مِثْلَيِ الْفَرِيضَةِ وَيَصُومُ مِنَ التَّطَوُّعِ مِثْلَيِ الْفَرِيضَةِ.
3. Ali ibn Ibrahim has narrated from his father from Ibn Abi ‘Umayr from ibn ’Udhaynah from ibn Fudayl ibn Yasar and al-Fadl ibn ‘Abd al-Malik and Bukayr who have said the following: “We heard abu ‘Abd Allah (a.s.), saying that the Messenger of Allah would perform of optional Salah (prayer) twice as much as obligatory Salah (prayer), and fast of optional fast twice as much as the obligatory one.”