Narrated `Abdullah bin `Umar: Allah's Apostle said, "The month (can be) 29 nights (i.e. days), and do not fast till you see the moon, and if the sky is overcast, then complete Sha'ban as thirty days."

Narrated Ibn `Umar: The Prophet said, "The month is like this and this," (at the same time he showed the fingers of both his hands thrice) and left out one thumb on the third time.

Narrated Abu Huraira: The Prophet or Abul-Qasim said, "Start fasting on seeing the crescent (of Ramadan), and give up fasting on seeing the crescent (of Shawwal), and if the sky is overcast (and you cannot see it), complete thirty days of Sha'ban."

Narrated Um Salama: The Prophet vowed to keep aloof from his wives for a period of one month, and after the completion of 29 days he went either in the morning or in the afternoon to his wives. Someone said to him "You vowed that you would not go to your wives for one month." He replied, "The month is of 29 days."

Narrated Anas: Allah's Apostle vowed to keep aloof from his wives for one month, and he had dislocation of his leg. So, he stayed in a Mashruba for 29 nights and then came down. Some people said, "O Allah's Apostle! You vowed to stay aloof for one month," He replied, "The month is of 29 days."

Imam Bukhari, may Allah have mercy on him, said that Ishaq bin Rahwayh said (in explanation of this) that even if they are less, still (in terms of reward) the reward of thirty days is given. Muhammad bin Sirin, may Allah have mercy on him, said (the meaning is) that both cannot be incomplete (twenty-nine days each) in one year.

Narrated Abu Bakra: The Prophet said, "The two months of `Id i.e. Ramadan and Dhul-Hijja, do not decrease (in superiority).

Narrated Ibn `Umar: The Prophet said, "We are an illiterate nation; we neither write, nor know accounts. The month is like this and this, i.e. sometimes of 29 days and sometimes of thirty days."

Narrated Abu Huraira: The Prophet said, "None of you should fast a day or two before the month of Ramadan unless he has the habit of fasting (Nawafil) (and if his fasting coincides with that day) then he can fast that day."

Narrated Al-Bara: It was the custom among the companions of Muhammad that if any of them was fasting and the food was presented (for breaking his fast), but he slept before eating, he would not eat that night and the following day till sunset. Qais bin Sirma-al-Ansari was fasting and came to his wife at the time of Iftar (breaking one's fast) and asked her whether she had anything to eat. She replied, "No, but I would go and bring some for you." He used to do hard work during the day, so he was overwhelmed by sleep and slept. When his wife came and saw him, she said, "Disappointment for you." When it was midday on the following day, he fainted and the Prophet was informed about the whole matter and the following verses were revealed: "You are permitted To go to your wives (for sexual relation) At the night of fasting." So, they were overjoyed by it. And then Allah also revealed: "And eat and drink Until the white thread Of dawn appears to you Distinct from the black thread (of the night)." (2.187)