Sayyiduna Abdullah bin Ja'far and Sayyiduna Abdullah bin al-Zubayr (may Allah be pleased with them) relate that the two of them came to the Messenger of Allah (peace and blessings be upon him) when each was seven years old. When he (peace and blessings be upon him) saw them, he smiled, stretched out his hand and took their pledge of allegiance.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13777