Musnad Abu Ya'la al-Mawsili 160:156

Yahya ibn Ayyub narrated to us, Ismail narrated to us, he said: Amr informed me, from Abu Sa'id, from Abu Hurayrah, he said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "How many a fasting person has no share of his fasting except hunger and thirst, and how many a person standing in prayer has no share of his standing except sleeplessness."