Kāmil al-Ziyārāt > The Ziyārah of Ĥusain (a.s.) Is Obligatory and Every Believer Should Fulfill this Obligation Toward Ĥusain and the Rest of the Imams (a.s.)
Hadith #2

2 حَدَّثَنِي أَبِي وَ أَخِي وَ عَلِيُّ بْنُ الْحُسَيْنِ وَ مُحَمَّدُ بْنُ الْحَسَنِ رَحِمَهُمُ اللَّهُ جَمِيعاً عَنْ أَحْمَدَ بْنِ إِدْرِيسَ عَنْ عُبَيْدِ اللَّهِ بْنِ مُوسَى عَنِ الْوَشَّاءِ قَالَ سَمِعْتُ الرِّضَا (ع) يَقُولُ إِنَّ لِكُلِّ إِمَامٍ عَهْداً فِي عُنُقِ أَوْلِيَائِهِ وَ شِيعَتِهِ وَ إِنَّ مِنْ تَمَامِ الْوَفَاءِ بِالْعَهْدِ وَ حُسْنِ الْأَدَاءِ زِيَارَةَ قُبُورِهِمْ فَمَنْ زَارَهُمْ رَغْبَةً فِي زِيَارَتِهِمْ وَ تَصْدِيقاً لِمَا رَغِبُوا فِيهِ كَانَ أَئِمَّتُهُمْ شُفَعَاءَهُمْ يَوْمَ الْقِيَامَةِ حَدَّثَنِي مُحَمَّدُ بْنُ يَعْقُوبَ الْكُلَيْنِيُّ عَنْ أَحْمَدَ بْنِ إِدْرِيسَ بِإِسْنَادِهِ مِثْلَهُ سَوَاءً

2. My father, my brother, ‘Ali ibn Ĥusain, and Muĥammad ibn Ĥasan all narrated to me from Aĥmad ibn Idrǐs, from ‘Ubaydillāh ibn Mūsā, from Al-Washā, who said: I heard Imam Riďā (a.s.) say: There is a binding contract on every Shia and follower toward his Imam and the most perfect and beautiful way to fulfill this contract is to go to the Ziyārah of the grave of that Imam. On the Day of Judgment, the Imams (a.s.) will intercede for those who go to their Ziyārah while longing for it and believing in that which they have been ordered to believe. The above Ĥadǐth has also been narrated to me through the following chain: Muĥammad ibn Ya’qūb Al-Kulayni, from Aĥmad ibn Idrǐs, from ‘Ubaydillāh ibn Mūsā, from Al-Washā, from Imam Riďā (a.s.).