Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) was offering prayer. When he went into prostration, Sayyiduna Imam Hasan (may Allah be pleased with him) and Sayyiduna Imam Husayn (may Allah be pleased with him) climbed onto his back. The people intended to stop the two of them, but the Prophet (peace and blessings be upon him) signalled to them to leave them be. When the Prophet (peace and blessings be upon him) completed the prayer, he seated them in his lap and said: "Whoever loves me should love these two."
Abu Ya'la and al-Bazzar recorded it, except that he (al-Bazzar) reported these words: When the Prophet (peace and blessings be upon him) completed the prayer, he (peace and blessings be upon him) hugged them close to himself.
Tabarani recorded it in abridged form. The narrators of Abu Ya'la are thiqat (trustworthy), though there is disagreement about some of its narrators.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 15065