Hadith 8:91
Muslim has something similar to the above from the Hadith of Jabir (RA), it goes:
"If he wishes he may eat, and if he wishes he may leave (the food alone)."
وَلَهُ مِنْ حَدِيثِ جَابِرٍ نَحْوُهُ . وَقَالَ : { فَإِنْ شَاءَ طَعِمَ وَإِنْ شَاءَ تَرَكَ }