Musnad Abu Ya'la al-Mawsili 42:245

Abu Khaythama narrated to us, Rawh ibn Aslam narrated to us, Hammad ibn Salama narrated to me, Sa'id al-Jariri informed us, from Abu Nadra, from Abu Sa'id al-Khudri: That the Messenger of Allah (may Allah bless him and grant him peace) asked Ibn Sayyad about the soil of Paradise. He said: "White flour, pure musk." The Messenger of Allah (may Allah bless him and grant him peace) said: "He has spoken the truth."