Those who reject al-Ghaybah ...

Sheikh al-Kuleyni in his great and blessed work of Kitab al-Kafi he narrate:

Chapter on al-Ghaybah.
(باب في الغيبة)

#4 ... From Sadir al-Sayrafi who has said the following: “I heard Abu Abdallah (as), say, ‘In the case of the person in charge of this task (i.e Imamah) there is a similarity to Yusuf (as).’ I then asked, ‘Are you, O Imam, speaking of his lifetime or his disappearance?’ The Imam then said to me, ‘Those who negate this (i.e al-Ghaybah) from this Ummah are like pigs.' The brothers of Yusuf were grandchildren of the prophets. They did business with Yusuf, conducted trade with him and spoke to him. They were his brothers and he was their brother but they could not recognize him until he said, I am Yusuf and this (Benjamin) is my brother. Why should (certain people of) this condemned nation refuse to accept if Allah, the Most Majestic, the Most Gracious, in a certain time would do to the possessor of His authority what He did to Yusuf? Yusuf was the person in charge of Egypt and there was a distance of twenty-eight days of journey between him and his father. If he wanted to inform him (his father) he could have done so. Jacob and his sons journeyed after they heard the good news, for nine days from their Bedouin home to Egypt. Why then should this nation refuse to accept if Allah, the Most Majestic, the Most Gracious, would do to the person who possesses His authority, what He did to Yusuf? That he may walk in their market place and step on their furnishings until Allah will grant him permission to reappear in public as He did to Yusuf as they asked, “Are you really Yusuf?” He said, “Yes, I am Yusuf.’”

4 - علي بن إبراهيم، عن محمد بن الحسين، عن ابن أبي نجران، عن فضالة بن أيوب، عن سدير الصيرفي قال: سمعت أبا عبد الله عليه السلام يقول: إن في صاحب هذا الامر شبها من يوسف عليه السلام، قال قلت له: كأنك تذكره حياته أو غيبته؟ قال: فقال لي: وما تنكر من ذلك، هذه الأمة أشباه الخنازير، إن إخوة يوسف عليه السلام كانوا أسباطا أولاد الأنبياء تاجروا يوسف، وبايعوه وخاطبوه، وهم إخوته، وهو أخوهم، فلم يعرفوه حتى قال: أنا يوسف وهذا أخي، فما تنكر هذه الأمة الملعونة أن يفعل الله عز وجل بحجته في وقت من الأوقات كما فعل بيوسف، إن يوسف عليه السلام كان إليه ملك مصر وكان بينه وبين والده مسيرة ثمانية عشر يوما، فلو أراد ان يعلمه لقدر على ذلك، لقد سار يعقوب عليه السلام وولده عند البشارة تسعة أيام من بدوهم إلى مصر، فما تنكر هذه الأمة أن يفعل الله عز وجل بحجته كما فعل بيوسف، أن يمشي في أسواقهم ويطأ بسطهم حتى يأذن الله في ذلك له كما أذن ليوسف، قالوا: " أئنك لانت يوسف؟ قال: أنا يوسف ".

- Usul al-Kafi, Vol.1, Page 336-337, Hadith Number 4.

According to Sheikh Hadi al-Najafi in his book Mawsu'at Ahadith Ahl al-Bayt (as), Vol.8, Page 229:
الرواية معتبرة الإسناد.
The Hadith has a well-based (Mu'tabirh i.e authentic) chain.

And according to Allamah al-Majlissi (rah) in Mirat al-Uqool, Vol.4, Page 37:
 (الحديث الرابع)

 (2): حسن
(Fourth Hadith)
(Hassan)