It is reported about Sayyiduna Abdullah bin al-Zubayr (may Allah be pleased with them both) and Sayyiduna Abdullah bin Ja'far (may Allah be pleased with him) that both of them gave the pledge of allegiance (bay'ah) to the Prophet (peace and blessings be upon him) at the age of seven. When the Prophet (peace and blessings be upon him) saw the two of them, he smiled, extended his blessed hand and took the pledge from both of them.
Imam al-Tabarani recorded this narration in al-Mu'jam al-Awsat and al-Mu'jam al-Kabir; its chain contains Isma'il bin Ayyash, about whom there is disagreement, and the rest of its narrators are the narrators of the Sahih.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 15538