Holy Quran, Chapter 9 Verse 3

وَأَذَانٌ مِّنَ اللّهِ وَرَسُولِهِ إِلَى النَّاسِ يَوْمَ الْحَجِّ الأَكْبَرِ أَنَّ اللّهَ بَرِيءٌ مِّنَ الْمُشْرِكِينَ وَرَسُولُهُ فَإِن تُبْتُمْ فَهُوَ خَيْرٌ لَّكُمْ وَإِن تَوَلَّيْتُمْ فَاعْلَمُواْ أَنَّكُمْ غَيْرُ مُعْجِزِي اللّهِ وَبَشِّرِ الَّذِينَ كَفَرُواْ بِعَذَابٍ أَلِيمٍ

“And an announcement from Allah and His Messenger to the people on the day of the greater pilgrimage that Allah and His Messenger are free from liability to the idolaters; therefore if you repent, it will be better for you, and if you turn back, then know that you will not weaken Allah; and announce painful punishment to those who disbelieve.”

Imam Jafar Sadiq (as) said, “This verse refers to the reappearance of al Mahdi (as) and the “announcement” refers to al Mahdi (as) inviting the people to Him.” (Tafseer Ayyashi volume 2 page  75)

• Read More: Mahdi in the Quran