It is narrated from Sayyiduna Taliq bin Ali, may Allah be pleased with him, that the Messenger of Allah, peace and blessings be upon him, said: Verily, Allah Almighty has made this moon a sign for the timings of people, so begin fasting by sighting the moon and end fasting by sighting it, and if the sky is cloudy, then complete the count to thirty.

It is narrated from Sayyiduna Abu Hurairah, may Allah be pleased with him, that the Messenger of Allah, peace and blessings be upon him, said: Begin fasting upon sighting the moon and stop fasting upon sighting the moon. However, if the moon is not visible due to clouds, then complete the count of thirty.

Syedna Jabir bin Abdullah (may Allah be pleased with him) has also narrated a similar hadith from the Noble Prophet (peace and blessings be upon him).

Abu Bakhtari says: We saw the crescent of Ramadan at the place of Dhat 'Irq, then we sent a man to Sayyiduna Abdullah bin Abbas (may Allah be pleased with him) to ask him about it. When he asked: Hashim says, then Sayyiduna Ibn Abbas (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: Allah Almighty has prolonged its sighting, if there are clouds then complete the counting (of Sha'ban).

Sayyiduna Abdullah bin Abbas (may Allah be pleased with him) says: I am astonished at the person who starts fasting before the month begins, while the Messenger of Allah (peace and blessings be upon him) has said: Do not fast until you see the moon.

A companion narrates that the Messenger of Allah, peace and blessings be upon him, said: Do not begin fasting before the month starts; rather, fast when the count of the previous month is completed or the new moon is sighted. Then continue fasting until the count of Ramadan is completed or the new moon is sighted.

Nafi’ narrates that it is reported from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: The month is (29) days, but do not begin fasting the month of Ramadan until you see the crescent, and do not stop fasting until you see (the Shawwal) crescent. If the sky is cloudy, then complete the count. Nafi’ says that the practice of Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) was that when it was the (29th) of Sha’ban, he would send some people to look for the crescent; if the crescent was sighted, that was best, and if it was not sighted and there was neither cloud nor dust, then he would not fast the next day. But if the sky was dusty or cloudy, then he would fast.

It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: The month is (29) days. Then, to explain, he struck one hand on the other twice and on the third time folded his thumb. In another narration: When people mentioned this to Sayyida Aisha (may Allah be pleased with her), she said: May Allah forgive Abu Abdur Rahman, Sayyiduna Ibn Umar (may Allah be pleased with him), he made a mistake. The real matter was that the Messenger of Allah (peace and blessings be upon him) had separated himself from his wives for a month, and on the (29th) day he came down (from the upper room). People said to him (peace and blessings be upon him): You have come down on the twenty-ninth day (even though you had separated for a month)? He (peace and blessings be upon him) said: Indeed, this month is (29) days.

It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: We are an unlettered nation; we neither know how to write nor how to calculate. The month is of such and such days, and such and such days, and such and such days. The third time, the Prophet (peace and blessings be upon him) folded his thumb (i.e., indicating 29 days). Then he said: The month is of such and such days, and such and such days, and such and such days, meaning a complete (30) days.