Al-Kāfi - Volume 4 > Months of al-Hajj
Hadith #3

3ـ عَلِيُّ بْنُ إِبْرَاهِيمَ بِإِسْنَادِهِ قَالَ أَشْهُرُ الْحَجِّ شَوَّالٌ وَذُو الْقَعْدَةِ وَعَشْرٌ مِنْ ذِي الْحِجَّةِ وَأَشْهُرُ السِّيَاحَةِ عِشْرُونَ مِنْ ذِي الْحِجَّةِ وَالْمُحَرَّمُ وَصَفَرُ وَشَهْرُ رَبِيعٍ الأَوَّلِ وَعَشْرٌ مِنْ شَهْرِ رَبِيعٍ الآخِرِ.

3. Ali has narrated through the same chain of his narrators has said the following: “He (the Imam) ‘Alayhi al-Salam, has said that the months of al-Hajj are Shawwal, Dhu al-Qa’dah and ten days of Dhu al-Hajj ah. The visiting months commence from twentieth of Dhu al-Hajj ah onward and includes the month of Muharram, Safar, Rabi’ al-Awwal and ten days of Rabi‘ al-Akhir.’”