Qatadah (may Allah have mercy on him) says: I asked Sa'id bin al-Musayyib (may Allah have mercy on him) how many people were at the Pledge of Ridwan. He said: There were fifteen hundred. I said: Jabir bin Abdullah (may Allah be pleased with them both) says fourteen hundred. He said: May Allah have mercy on him, he was mistaken; he himself told me that they were fifteen hundred.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10199