Musnad Abu Ya'la al-Mawsili 155:7

Ahmad ibn Jamil al-Marwazi narrated to us, from Marwan ibn Mu'awiyah, from Yasin ibn Mu'adh al-Zayyat, from al-Zuhri, from Sa'id ibn al-Musayyib, from Abu Hurayrah, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Whoever embraces Islam while possessing something, it belongs to him."