Abu Huraira related that the Prophet (pbuh) said: Whoever fasts during Ramadan with faith and seeking his reward from Allah will have his past sins forgiven. Whoever prays during the nights in Ramadan with faith and seeking his reward from Allah will have his past sins forgiven. And he who passes Lailat al-Qadr in prayer with faith and seeking his reward from Allah will have his past sins forgiven (Bukhari, Muslim).
Abu Huraira related that Rasulullah (saw) said: If anyone omits his fast even for one day in Ramadan without a concession or without being ill, then if he were to fast for the rest of his life he could not make up for it (Bukhari).
Abu Huraira related that the Prophet (pbuh) said: Allah the Majestic and Exalted said: “Every deed of man will receive ten to 700 times reward, except Siyam (fasting), for it is for Me and I shall reward it (as I like). There are two occasions of joy for one who fasts: one when he breaks the fast and the other when he will meet his Lord” (Muslim).
Abu Huraira related that Rasulullah (saw) said: Many people who fast get nothing from their fast except hunger and thirst, and many people who pray at night get nothing from it except wakefulness (Darimi).
When to start fasting
Ibn Umar related that the Prophet (pbuh) said: Do not start fasting unless you see the new moon, and do not end fasting until you see it. If the weather is cloudy then calculate when it should appear (Bukhari, Muslim).
The Suhoor meal (which is eaten before dawn)
Anas related that Rasulullah (saw) said: Take the Suhoor meal, for there is blessing in it (Bukhari, Muslim).
Breaking your fast
Salman ibn Amir Dhabi related that the Prophet (pbuh) said: Break your fast with dates, or else with water, for it is pure (Abu Dawud, Tirmidhi).
Fasting during a journey
Aisha related that Rasulullah (saw) was asked whether one should fast when on a journey, and he replied: Fast if you like, or postpone it if you like (Bukhari, Muslim).
Behavior while fasting
Abu Huraira related that the Prophet (pbuh) said: If a person does not avoid false talk and false conduct during Siyam, then Allah does not care if he abstains from food and drink (Bukhari, Muslim).
Forgetfully eating or drinking while fasting
Abu Huraira related that Rasulullah (saw) said: If anyone forgets that he is fasting and eats or drinks he should complete his Siyam, for it is Allah who has fed him and given him drink (Bukhari, Muslim).
Providing for those who are breaking the fast
Zaid ibn Khalid Juhni related that the Prophet (pbuh) said: He who provides for the breaking of the Siyam of another person earns the same merit as the one who was observing Siyam diminishing in any way the reward of the latter (Tirmidhi)
And Allah knows best.
