The Book of Drinks (Kitab Al-Ashriba)
Muslim :: Book 23 : Hadith 5060
Anas b Malik reported: Abu Talha sent me to Allah's Messenger (may peace be upon him) ; the rest of the hadith is the same, but 'there is a slight variation of wording that he said at the end (The Holy Prophet) took what was left (of the food) and collected it and then invoked blessings upon it and it returned to its original state. He (the Holy Prophet) then said Take this.