Al-Kāfi

Hadith 1739
4ـ مُحَمَّدُ بْنُ يَحْيَى عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنْ مُحَمَّدِ بْنِ سِنَانٍ عَنِ ابْنِ مُسْكَانَ عَنْ مُحَمَّدِ بْنِ أَبِي عُمَيْرٍ قَالَ سَأَلْتُ أَبَا عَبْدِ الله (عَلَيْهِ الْسَّلام) عَنْ أَفْضَلِ مَا جَرَتْ بِهِ السُّنَّةُ مِنَ الصَّلاَةِ فَقَالَ تَمَامُ الْخَمْسِينَ. وَرَوَى الْحُسَيْنُ بْنُ سَعِيدٍ عَنْ مُحَمَّدِ بْنِ سِنَانٍ مِثْلَهُ.
4. Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from Muhammad ibn Sinan from ibn Muskan from Muhammad Ibn Abi ‘Umayr who has said the following: “I once asked abu ‘Abd Allah (a.s.), about the most excellent item in the Sunnah of Salah (prayer). He (the Imam) said, ‘It is the complete, all fifty (Rak‘at).’” Al-Husayn ibn Sa‘id has narrated from Muhammad ibn Sinan a similar Hadith.
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī