Sahih al-Bukhari, Hadith no. 1894
“nahi hoon. to is is sense mein kaha ke woh kahe ke mein rozay daar hoon, mein rozay daar hoon. aise hi ek lambi hadees hai, is ke aakhir mein aata hai "الصيام لی وانا اجزبہ." yeh bhi bohat achhi hadees hai ke roza mere liye ALLAH taala ne farmaya, khud apne ah apne ah taraf nisbat ki is ki ke roza mere liye hai "and I will give the reward." yani is ka reward mein khud hi doonga.”