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 #4

4 حَدَّثَنِي أَبِي وَ مُحَمَّدُ بْنُ الْحَسَنِ رَحِمَهُمُ اللَّهُ جَمِيعاً عَنِ الْحَسَنِ بْنِ مَتِّيلٍ عَنِ الْحَسَنِ بْنِ عَلِيٍّ الْكُوفِيِّ عَنْ عَلِيِّ بْنِ حَسَّانَ الْهَاشِمِيِّ عَنْ عَبْدِ الرَّحْمَنِ بْنِ كَثِيرٍ مَوْلَى أَبِي جَعْفَرٍ (ع) عَنْ أَبِي عَبْدِ اللَّهِ (ع) قَالَ لَوْ أَنَّ أَحَدَكُمْ حَجَّ دَهْرَهُ ثُمَّ لَمْ يَزُرِ الْحُسَيْنَ بْنَ عَلِيٍّ (ع) لَكَانَ تَارِكاً حَقّاً مِنْ حُقُوقِ اللَّهِ وَ حُقُوقِ رَسُولِ اللَّهِ (ص) لِأَنَّ حَقَّ الْحُسَيْنِ (ع) فَرِيضَةٌ مِنَ اللَّهِ وَاجِبَةٌ عَلَى كُلِّ مُسْلِمٍ

4. My father and Muĥammad ibn Ĥasan both narrated to me from Ĥasan ibn Mattǐl, from Ĥasan ibn ‘Ali Al-Kūfi, from ‘Ali ibn Ĥassān Al-Hāshimi, from ‘Abdil Raĥmān ibn Kuthayr – the servant of Abǐ Ja’far (Imam Bāqir (a.s.)), who said: Abū ‘Abdillāh (Imam Šādiq (a.s.)) said: Even if you go to Hajj every year of your life but do not go to the Ziyārah of Ĥusain ibn ‘Ali (a.s.), you have abandoned one of your obligations toward Allāh and His Messenger (s.a.a.w.). Verily Allāh has made it mandatory (on the believers to fulfill) the right(s) of Ĥusain (a.s.), and this (Ziyārah) is obligatory on every Muslim.