Shaykh of shias Ibn Qawlaweyh in his “al-Kamil az-Ziyarat” (p 114) narrated from Abu Jafar that prophet (sallalahu alaihi wa ala alihi wa sallam) said:

 من اراد ان يتمسك بعروة الله الوثقي التي قال الله تعالى في كتابه ، فليوال علي بن ابي طالب والحسن والحسين ( عليهم السلام )، فان الله يحبهما من فوق عرشه.

Translation:

Whoever wish to attach to firmest handle which is mentioned by Allah Taala in his Book, should befriend with Ali ibn Abu Talib and al-Hasan and al-Husayn (alaihuma salam), because ALLAH LOVES THEM FROM ABOVE THE THRONE.

At page 278 he narrated:

عن زيد الشحام ، قال : قلت لابي عبد الله ( عليه السلام ) : ما لمن زار قبر الحسين ( عليه السلام ) ، قال : كان كمن زار الله في عرشه ، قال : قلت : ما لمن زار احدا منكم ، قال : كمن زار رسول الله  صلى الله عليه وآله .

Translation:

From Zayd ash-Shaham: I said to Abu Abdullah (alaihi salam): What is for the one who visited  grave of Husayn (alaihi salam)? He said: It is like a visit of Allah on His Arsh. I said: And what for those who visited one of them? He said: It is like a visit of prophet (sallalahu alaihi wa ali)

And at page 320, ibn Qawlaweyh narrated that Imam Abu Abdullah said:

من زار الحسين ( عليه السلام ) يوم عرفة كان كمن زار الله في عرشه.

Translation:

Who visited Husayn (alaihi salam) on the day of Arafah like visited Allah on His Arsh.

من زار قبر الحسين بن علي ( عليهما السلام ) عارفا بحقه كان كمن زار الله في عرشه.

Translation:

Who has visited Husayn (alaihi salam) and he knows his rights, like visited Allah on His Throne.