Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates: Whenever a man came to the Prophet (peace and blessings be upon him) and said: "I am obliged to free a slave from the descendants of Isma'il," the Prophet (peace and blessings be upon him) would say: "Take Hasan and Husayn (as your example)."
Al-Tabarani recorded it, and its narrators are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 15100