"Forty Ahadith on Ghadir" by Mahmud Sharifi
Hadith no. 1: The 'Eid of the Khilafat and Wilayat
رَوى زِيَادُ بْنُ مُحَمَّدٍ قَالَ: دَخَلْتُ عَلى أَبِي عَبْدِ اللٌّهِ فَقُلْتُ: لِلْمُسْلِمِينَ عِيْدٌ غَيْرُ يَوْمِ الْجُمُعَةِ وَالْفِطْرِ وَالأَضْحى؟ قَالَ: نَعَمْ، أَلْيَوْمُ الَّذِي نَصَبَ فِيهِ رَسُولُ اللٌّهِأَمِيـرَ الْمُؤْمِنِينَ
It has been narrated from Ziyad ibn Muhammad that he said, “I went to see Abi 'Abdillah [Ja'far ibn Muhammad as-Sadiq] (peace be upon him) and said to him, “Do the Muslims have an 'Eid other than the day of Jumu'ah and al-Fitr and al-Adhha?” The Imam (peace be upon him) replied to me, “Yes, the day which the Messenger of Allah (blessings of Allah be upon him and his family) appointed Amirul Mo’minin (peace be upon him) [as the leader of the Ummah after him].”