Abdullah Ibn Abbas informed: I saw the Messenger of Allah (s.a.w.a.) and his companions in Mina. Hassaan Ibn Thabet (the Prophet’s s.a.w.a. poet) was amongst them.

The Messenger of Allah (s.a.w.a.) announced – O Muslims! This is Ali Ibn Abi Talib (a.s.). He is the master of Arabs and he is the greatest successor. He is to me like Harun was to Musa, except that there is no prophet after me. Repentance will not be accepted from anyone except through the love for Ali Ibn Abi Talib (a.s.).

Then the Prophet turned to Hassaan and instructed – O Hassaan, recite a poem about Ali.

Hassaan recited:

لَا تُقْبَلُ التَّوْبَةُ مِنْ تَائِبٍ‏ إِلَّا بِحُبِّ ابْنِ أَبِي طَالِبٍ‏
أَخُو رَسُولِ اللَّهِ بَلْ صِهْرُهُ‏ وَ الصِّهْرُ لَا يَعْدِلُ بِالصَّاحِبِ‏
وَ مَنْ يَكُنْ مِثْلَ عَلِيٍّ وَ قَدْ رُدَّتْ لَهُ الشَّمْسُ مِنَ الْمَغْرِبِ‏

رُدَّتْ عَلَيْهِ الشَّمْسُ فِي ضَوْئِهَا بَيْضاً كَأَنَّ الشَّمْسَ لَمْ تَغْرُب‏

Repentance will not be accepted from the repenting one
Except through the love for the Son of Abi Talib (a.s.).
He is the brother of the Messenger of AlIah (s.a.w.a.), rather his son-in-law
And the son-in-law cannot be equated with a companion
And who can be like Ali? And surely
The sun returned for him after sunset
The sun returned for him with its brilliance
Shining bright, as if the sun had never set
Bashaarah al-Mustafa Le Shiah al-Murtaza v 2 p 147-148 Behaar al-Anwaar v 37 p 260