Al-Hussein ibn Ali (peace upon him) said (addressing his killers):

"Is it right for you to kill the likes of me, when I am the son of the daughter of your Messenger, and there is no one on the face of this earth who is the son of a daughter of a Messenger [of God] except me?!" [1, 3]

Shaykh al-Islam ibn Taymiyah (may Allah shower him with Mercy) said:

"As for he who killed al-Hussein, or assisted in his killing, or was pleased by it, then upon him is the curse of Allah, and His Angels, and the people altogether." [2-3]

Reference:

[1] Al-Bidaya wa Al-Nihaya by Ibn Katheer 8/193; Al-Jaza’ min Jins al-‘Amal by Sayed Affani 2/162

[2] Majmou’ Al-Fataawa by Ibn Taymiyah 4/487

[3] Benefited from Sh. Abu Laila Al-Baqellany: https://www.facebook.com/ALBaQeLLany/posts/857921097635724

مؤلمة

قال الحسين عليه السلام مخاطبا قتلته: "هل يصلح لكم قتال مثلي، وأنا ابن بنت نبيكم، وليس على وجه الأرض ابن بنت نبي غيري؟"ـ

قال شيخ الإسلام رحمه الله: "فأما من قتل الحسين، أو أعان على قتله، أو رضي بذلك، فعليه لعنة الله وملائكته والناس أجمعين"ـ

Hussein-Bin-Ali-Name[1]