Hadith.1940 - Muhammad ibn Abi Umayr narrated from Mu'awiyah ibn Ammar, who said
"I asked Abu Abdullah (as): 'I instruct a servant girl to check for the dawn, and she tells me that it has not risen yet, so I eat. Then I check and find that it had actually risen when she looked.'
Imam (as) said: 'Make up that day. However, if you had been the one to check and it happened, there would be nothing upon you.'"