Musnad Ahmad 30:2816

'Abd al-Rahman narrated to us, he said: Sulaym ibn Hayyan narrated to us, from Sa'id, he said: I heard Abu Hurayrah, he said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The change in the breath of the fasting person is more pleasant to Allah than the scent of musk." Bahz said: On the Day of Resurrection.