Sahih Muslim
This hadith has been narrated on the authority of Sufyan with the same chain of transmitters in which it is said:" Fasting of two months."
وَحَدَّثَنِيهِ إِسْحَاقُ بْنُ مَنْصُورٍ، أَخْبَرَنَا عُبَيْدُ اللَّهِ بْنُ مُوسَى، عَنْ سُفْيَانَ، بِهَذَا الإِسْنَادِ وَقَالَ صَوْمُ شَهْرَيْنِ .
Grade: Sahih
صحيح
Reference