Fiqh-us-Sunnah Volume 3, Zakaat and Fasting, Fiqh 3.130.

All Muslims agree that it is preferred to eat a pre-dawn meal and that there is no sin upon one who does not do so. Anas reported that the Messenger of Allah said: “Eat a pre-dawn meal, for there are blessings in it.” This is related by alBukhari and Muslim.

Al-Miqdam ibn Madyakrib reported that the Prophet, upon whom be peace, said: “You should eat this pre-dawn meal for it is a blessed nourishment.” This is related by an-Nasa’i with a good chain. The reason why it is a blessing is that it strengthens the fasting person, makes him more energetic, and makes the fast easier for him.