Musnad Abu Ya'la al-Mawsili 115:309

Narrated to us Ubayd Allah, narrated to us Khalid ibn al-Harith, narrated to us Sa'id, from Qatadah, from Anas, from the Prophet (peace and blessings of Allah be upon him), who said: "Eat the pre-dawn meal (suhur), for indeed there is blessing in the pre-dawn meal."