Imam Muhammad Baqir (asws) narrates:

“Order Our Shia to perform the Ziarat of the grave of Hussain (asws). Performing His Ziarat is wajib upon every momin who testifies that Hussain (asws) is an Imam divinely appointed by Allah (swt).” 
Ref. Kamil ul Ziaraat

Salim ibn Mukram al Jamal narrates:

I asked Aba Abdullah Imam Jafar Sadiq (asws) regarding the Ziarat of the grave of Hussain (asws).
Imam (asws) replied, “It is the best of all deeds.”
Ref. Kamil ul Ziaraat

Imam Jafar Sadiq (asws) narrates:
“The zawir (visitor) of Hussain (asws) ibn Ali (asws) is the zawir of RasoolAllah (saw).”
Ref. Kamil ul Ziaraat

Imam Jafar Sadiq (asws) narrates:
“Performing the Ziarat of the grave of Hussain (asws) is the most beloved of all deeds by Allah. And the action that Allah likes the most is when one momin helps another momin. And the nearest a slave can get to Allah is when he performs sajda while crying.”
Ref. Kamil ul Ziaraat

Abu Usamah narrates:
I heard Aba Abdullah Imam Jafar Sadiq (asws) say:
“Those who wish to be raised near the station of their Prophet (saw), Ameerul Momineen (asws), and Syeda Fatima (sa) should not neglect performing the Ziarat of Hussain (asws) ibn Ali (asws).”
Ref. Kamil ul Ziaraat

Abu Baseer narrates:
I heard Aba Abdullah Imam Muhammad Baqir (asws) say, “Those who wish for their final abode to be Jannah should not neglect performing the Ziarat of the Oppressed One.”
I asked, “Who is the Oppressed One?”
Imam (asws) replied, “Hussain (asws) ibn Ali (asws), the Man of Karbala. Allah will make those who perform His Ziarat while longing for Him and with love for RasoolAllah (saw), love for Syeda Fatima (sa), and love for Ameerul Momineen (asws) to sit at the Ma’ida (table spread) of Jannah. They will be dining with them while others are facing the Hasab (accountability).”
Ref. Kamil ul Ziaraat

Abu Usama Zaid al Shaham narrates:

I heard Aba Abdullah Imam Jafar Sadiq (asws) say, “Allah will record those who perform the Ziarat of the grave of Hussain (asws) while having a strong desire to visit Imam Hussain (asws) in their heart amongst those who will be safe on the Day of Judgment. He will give them their book of deeds in their right hands and they will be under the flag of Hussain (asws) until they enter Jannah. Hussain (asws) will make them dwell at His station in Jannah. Allah is all Mighty and Wise.”
Ref. Kamil ul Ziaraat

Abdullah ibn Zurarah narrates:
I heard Aba Abdullah Imam Jafar Sadiq (asws) say, “On the Day of Judgment those who have performed the Ziarat of Hussain (asws) ibn Ali (asws) will be given preference over others.”

I asked, “What kind of preference?”

Imam (asws) replied, “They will enter Jannah forty years before others do. They will enter Jannah whilst others will be waiting in the Desert of Judgment to face the Hasab (accountability).”
Ref. Kamil ul Ziaraat

Imam Muhammad Baqir (asws) narrates:
“Inform Our Shia to perform the Ziarat of the grave of Hussain (asws). Performing His Ziarat increases rizq (sustenance), prolongs life, and keeps afflictions away. Performing His Ziarat is wajib upon every momin who believes Hussain (asws) has been divinely appointed by Allah as an Imam.”
Ref. Kamil ul Ziaraat

Imam Musa Kazim (asws) narrates:
“The least reward for those who perform the Ziarat of Hussain (asws) by the banks of the River Furat whilst having His marifat and believing in His Glory and Wilayat is their past and future sins will be forgiven.”
Ref. Kamil ul Ziaraat

Imam Musa Kazim (asws) narrates:
“The least reward for those who perform the Ziarat of Hussain (asws) by the shores of the River Furat whilst having His marifat and believing in His greatness and Wilayat is the forgiveness for all of their past and future sins.”
Ref. Kamil ul Ziaraat

Muhammad ibn Abu Jareer al Qummi narrates:
I heard Abul Hasan Imam Reza (asws) say to my father, “Those who perform the Ziarat of Hussain (asws) ibn Ali (asws) whilst having His marifat will be speaking with Allah on top of His Arsh on the day of judgment. “Surely those who guard (against evil) shall be in gardens and rivers, In an Assembly of Truth, in the Presence of a Sovereign Omnipotent.” (Quran 54:54-55)
Ref. Kamil ul Ziaraat

Al Washa narrates:
I heard Imam Reza (asws) say:
“There is a binding contract upon every Shia towards His Imam. The most perfect and beautiful way to fulfill this contact is by performing the Ziarat of the grave of that Imam. On the Day of Judgment the Imams (asws) will intercede for those who performed Their Ziarat while having longed to perform ziarat and while believing in all they have been ordered to believe in.”
Ref. Kamil ul Ziaraat

Um Sa’eed al Ahmasiya narrates:

Imam Jafar Sadiq (asws) asked me, “O’ Um Sa’eed! Do you perform the Ziarat of the grave of Hussain (asws)?” I replied, “Yes.”
Imam (asws) replied, “Perform His Ziarat. For performing the ziarat of the grave of Hussain (asws) is wajib on both men and women.”
Ref. Kamil ul Ziaraat

Abdul Rahman ibn Kuthair (servant of Imam Muhammad Baqir asws) narrates:

Imam Jafar Sadiq (asws) said:
“Even if you go for Hajj every year of your life but you do not perform the Ziarat of Hussain (asws) ibn Ali (asws) then you have abandoned one of your wajibats (obligations) towards Allah and His Messenger (saw).
Allah has made it wajib on the momin to fulfill the rights of Hussain (asws) and this Ziarat is wajib upon every Muslim”.
Ref. Kamil ul Ziaraat