Ibn Shihab (may Allah have mercy on him) and other scholars said: On the day of Uhud, he (peace and blessings be upon him) set out with a thousand men. When they reached al-Shawt, between Madinah and Uhud, Abdullah bin Ubayy the hypocrite broke away with a third of the people, and the people of doubt and the hypocrites who followed him went back.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 17860