Abu Tha'laba al-Khushani reported Allah's Messenger ﷺ as saying, “Allah has made certain things binding, so do not cause them to be lost; He has prohibited certain things, so do not violate them; He has fixed certain limits, so do not transgress them; and He, without being forgetful, has said nothing about certain things, so do not search into them.” Daraqutni transmitted it.

Abu Huraira reported Allah's Messenger ﷺ as saying, “Fast when you see it and break your fast when you see it, and if the weather is cloudy treat Sha‘ban as having thirty days.” (Bukhari and Muslim.)

Ibn ‘Umar reported Allah's Messenger ﷺ as saying, “We are an unlettered people who can neither write nor count. The month is thus and thus and thus,” drawing in his thumb when he said it the third time.* Then he said, “The month is thus and thus and thus,” meaning a complete thirty days. He meant alternately twenty-nine and thirty. *Spreading out the ten fingers the first two times and nine the third time. (Bukhari and Muslim.)

Abu Bakra reported Allah's Messenger ﷺ as saying, “The months of festival, Ramadan and Dhul-hijja, are not defective.”* *The most probable meaning is that, even if these months have only twenty-nine days, they are not on that account to be considered deficient in comparison with a month which has thirty days. (Bukhari and Muslim.)

Abu Huraira reported Allah's Messenger ﷺ as saying, “None of you must fast one day or two days just before Ramadan, except in the case of a man who has been in the habit of observing a particular fast, for he may fast on that day.”* *If a man is in the habit of fasting on a particular day of the week and one or other of the two days before Ramadan falls on that day, he may observe his usual practice. (Bukhari and Muslim.)

Abu Huraira reported Allah's Messenger ﷺ as saying, "When the middle of Sha'ban comes do not fast." Abu Dawud, Tirmidhi, Ibn Majah and Darimi transmitted it.

He reported Allah's Messenger ﷺ as saying, "Calculate on the basis of the new moon of Sha'ban when Ramadan begins." Tirmidhi transmitted it.

Umm Salama said she never saw the Prophet (ﷺ) fasting two consecutive months, except Sha'ban and Ramadan. Abu Dawud, Tirmidhi, Nasa’i and Ibn Majah transmitted it.

‘Ammar b. Yasir said, "He who fasts on a day about which he is doubtful has disobeyed Abul Qasim"* *i.e., the Prophet. Abu Dawud, Tirmidhi, Nasa’i, Ibn Majah and Darimi transmitted it.

Ibn ‘Abbas told a desert Arab coming to the Prophet (ﷺ) and saying he had seen the new moon, i.e. the new moon of Ramadan. He asked him whether he testified that there is no Allah but Allah and he replied that he did. He then asked if he testified that Muhammad is Allah's Messenger ﷺ, and when he replied that he did he said, “Bilal, announce to the people that they must fast tomorrow." Abu Dawud, Tirmidhi, Nasa’i, Ibn Majah and Darimi transmitted it.

Ibn ‘Umar said that the people tried to see the new moon and he informed Allah's Messenger ﷺ that he had seen it, so he fasted and commanded the people to observe the fast." Abu Dawud and Darimi transmitted it.