It is disliked for a fasting person to eat if he doubts the dawn has broken; because it is possible that dawn has indeed broken, and eating would invalidate the fast, so he should avoid it. This is based on his saying, peace be upon him: "The lawful is clear and the unlawful is clear, and between them are ambiguous matters, so leave what causes you doubt for what does not cause you doubt," as found in Sunan al-Nasa'i al-Kubra 3: 468, Al-Mujtaba 8: 230, Musannaf Ibn Abi Shaybah 4: 544, and Sunan al-Bayhaqi al-Kabir 10: 115. Also, his saying, peace be upon him: "Indeed, every king has a sanctuary, and the sanctuary of Allah is His prohibitions," as found in Sahih al-Bukhari 1: 28 and Sahih Muslim 3: 1219. The one who eats while doubting the dawn is circling around the sanctuary and is close to falling into it, thus by eating he is exposing his fast to invalidation, so it is disliked for him. If he eats while in doubt, he is not required to make up the fast merely due to doubt; because the invalidation of the fast is uncertain, given the doubt about the dawn, and the original state is the continuation of the night. Daylight is not established by doubt, except if he is certain that it has risen, then he must make up the fast. Similarly, if he has eaten before dawn and is certain that dawn has not yet broken, he does not have to make up the fast according to the correct opinion; because he is certain of the night, and it is only invalidated by certainty of a similar nature. See: Bada'i' al-Sana'i' 2: 105.