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:

عن أبي جعفر (ع) قال: لما قتل جدي الحسين (ع) ضجت الملائكة إلى الله عز وجل بالبكاء والنحيب، وقالوا: إلهنا وسيدنا انتقم ممن قتل صفوتك وابن صفوتك‏ وخيرتك من خلقك، فأوحى الله عز وجل إليهم: قروا ملائكتي فو عزتي وجلالي لأنتقمن منهم ولو بعد حين. ثم كشف الله عز وجل عن الأئمة من ولد الحسين (ع) للملائكة فسرت الملائكة بذلك فإذا أحدهم قائم يصلي، فقال الله عز وجل: بذلك أنتقم منهم‏.

Imam Mohammad Al-Baqir (ع) said:

"When my grandfather Al-Husain (ع) was killed, the angels raised an uproar with tears and weeping. They said: “O our Allah and our Master, take your revenge from those who killed Your chosen one and the son of Your chosen one and Your greatest one among Your creatures."

Thus Allah revealed to them: "Calm down My angels. Indeed I will take My revenge from them even if after a while. Then Allah uncovered the Imams from the descendants of Husain (ع) and the angels were gladdened for seeing them. One of them was standing (Qaim) in prayer. Allah told them: "By this one, I will take My revenge from them."

[Source: Elal al-Sharae, Shaikh Sadooq, Vol. 1, pg. 160]