Hadith 1:

On his way to Karbala, Imam Husain (ع) said to his Son:

 يَا وَلَدِي يَا عَلِيُّ وَ اللَّهِ لَا يَسْكُنُ دَمِي حَتَّى يَبْعَثَ اللَّهُ الْمَهْدِيَّ فَيَقْتُلَ عَلَى دَمِي مِنَ الْمُنَافِقِينَ الْكَفَرَةِ الْفَسَقَةِ سَبْعِينَ أَلْفاً

"O My Son Ali, by Allah, My blood will not be at rest until Allah sends the Mahdi (ع) who will kill a thousand of disbelieving sinful Hypocrites taking revenge for My blood"

[Source: al-Manaqib, Ibn Shehr Ashoob, Vol. 4, Pg. 85]

Hadith 2:

قُلْتُ فَلِمَ سُمِّيَ الْقَائِمُ قَائِماً قَالَ لَمَّا قُتِلَ جَدِّيَ الْحُسَيْنُ(ع)ضَجَّتْ عَلَيْهِ الْمَلَائِكَةُ إِلَى اللَّهِ تَعَالَى بِالْبُكَاءِ وَ النَّحِيبِ وَ قَالُوا إِلَهَنَا وَ سَيِّدَنَا أَ تَغْفَلُ عَمَّنْ قَتَلَ صَفْوَتَكَ وَ ابْنَ صَفْوَتِكَ وَ خِيَرَتِكَ مِنْ خَلْقِكَ فَأَوْحَى اللَّهُ عَزَّ وَ جَلَّ إِلَيْهِمْ قَرُّوا مَلَائِكَتِي فَوَ عِزَّتِي وَ جَلَالِي لَأَنْتَقِمَنَّ مِنْهُمْ وَ لَوْ بَعْدَ حِينٍ ثُمَّ كَشَفَ اللَّهُ عَزَّ وَ جَلَّ عَنِ الْأَئِمَّةِ مِنْ وُلْدِ الْحُسَيْنِ(ع) لِلْمَلَائِكَةِ فَسُرَّتِ الْمَلَائِكَةُ بِذَلِكَ فَإِذَا أَحَدُهُمْ قَائِمٌ يُصَلِّي فَقَالَ اللَّهُ عَزَّ وَ جَلَّ بِذَلِكَ الْقَائِمُ أَنْتَقِمُ مِنْهُمْ

Part of a long narration from Abu Hamzah Thumali in which Abu Hamzah asks Imam Baqir (عليه السلام):

"Why was al-Qaim (the one who rises) named al-Qaim?"

The Imam replied, "When my grandfather al-Husayn (عليه السلام) was killed, the angels cried out to Allah (تعالى) with weeping and lamentation. They said, 'Our Allah and our Master! Do You overlook those who killed Your chosen one, the son of Your chosen one, and the best of Your creation?'

Then Allah (عز وجل) inspired them: 'Be at ease, My angels. By My Might and My Majesty, I will surely take revenge upon them, even if it is after some time.'

Then Allah (عز وجل) unveiled the Imams from the descendants of al-Husayn (عليه السلام) to the angels. The angels rejoiced at this, and one of them was standing (Qaim) in prayer.

Allah (عز وجل) said, "Through that standing one (al-Qaim), I will take revenge upon them."

(Source: ilal al-Sharae, Shaikh Saduq, Vol. 1, Ch. 129, Hadith. 1) 

Hadith 3:

From Ziyarat Ashura as taught by Imam Baqir (عليه السلام):

فَأَسْأَلُ اللَّهَ الَّذِي أَكْرَمَ مَقَامَكَ أَنْ يُكْرِمَنِي بِكَ وَ يَرْزُقَنِي طَلَبَ ثَارِكَ مَعَ إِمَامٍ مَنْصُورٍ مِنْ آلِ مُحَمَّدٍ (ص)

"So I ask Allah, Who has honored your station, to honor me through you, and to grant me the opportunity to seek your vengeance/revenge along with a victorious Imam from the family of Muhammad (صلى الله عليه وآله)."

[Source: Kamil al-Ziyarat, Ch. 71, Hadith. 8]