It is narrated from Sayyiduna Abu Ayyub al-Ansari (may Allah be pleased with him); he said: I prepared food for the Prophet (peace and blessings be upon him) and Abu Bakr (may Allah be pleased with him), enough to suffice the two of them, and took it to them. The Messenger of Allah (peace and blessings be upon him) said to me: "Go and invite thirty of the notables of the Ansar to me." This weighed heavily upon me; I said (to myself): I have nothing more than this. It was as if I became somewhat inattentive, so he (peace and blessings be upon him) said again: "Go and invite thirty of the notables of the Ansar to me." So I invited them, and when they came he (peace and blessings be upon him) said: "Eat." They ate until they were satisfied and left; then they testified that he was the Messenger of Allah, and pledged allegiance to him before going out. Then he (peace and blessings be upon him) said: "Go and invite sixty of the notables of the Ansar to me." Abu Ayyub (may Allah be pleased with him) said: By Allah, inviting sixty felt even easier to me than thirty. So I invited them, and the Messenger of Allah (peace and blessings be upon him) said: "Wait a little." They ate until they were satisfied and left; then they testified that he was the Messenger of Allah, and pledged allegiance to him before going out. Then he (peace and blessings be upon him) said: "Go and invite ninety of the Ansar to me." (Abu Ayyub (may Allah be pleased with him)) said: Now inviting ninety and sixty felt even easier to me than thirty. So I invited them, and they ate until they were satisfied and left; then they testified that he was the Messenger of Allah, and pledged allegiance to him before going out. Thus one hundred and eighty men ate from that food of mine, all of them from the Ansar.
Hadith Referenceالمعجم الكبير للطبراني / باب الخاء / 4075