Abu Bakrah, may Allah be pleased with him, narrated that the Prophet, sallallaahu ‘alayhi wa salam, said: “Two months of ‘Eed are not incomplete: the months of Ramadan and Thul-Hijjah.” According to another version: “Two months of ‘Eed are not shorter [than normal]: Ramadan and Thul-Hijjah.” [Al-Bukhari and Muslim]
In explanation of this Hadeeth, it is said that, in one year, both the months of Ramadan and Thul-Hijjah cannot be incomplete together. This means that if one of them is short [i.e., of 29 days], the other, more often than not, would be complete [i.e., 30 days].
This Hadeeth was also interpreted to mean that the reward of observing acts of worship in them is not decreased, even if the number of days is less than normal. This is believed to be closer to the intended meaning.
Benefits and rulings [derived from these Hadeeths]
First: The Prophet favored both months of Ramadan and Thul-Hijjah with this ruling, in view of them being the two [blessed] months of fasting and Hajj (major pilgrimage), respectively.
Second: It is permissible to link ‘Eed Al-Fitr to Ramadan, although it is on the first day of Shawwaal. The following Hadeeth supports this: “Two months are not incomplete [together], in each of which there is ‘Eed: Ramadan and Thul-Hijjah.” [Ahmad]
Third: Erring in determining the beginning of the month is probable, but no sin will be incurred if people follow the Sharee‘ah (Islamic jurisprudence) by anticipating the birth of the new moon and, in case it is not visible, calculating the month by completing it [to thirty days].
Fourth: All merits and rulings of the two months of Ramadan and Thul-Hijjah are consistent, regardless if the length of Ramadan is 29 or 30 days; and whether or not standing on ‘Arafah actually coincides with the ninth day of Thul-Hijjah, provided that adequate effort was exerted to sight the new moon [at the beginning of the month].
Fifth: The main benefit of this Hadeeth is to remove doubt or sadness for those who fast only twenty-nine days or mistakenly stand at ‘Arafah on a day other than the ninth, such as the eighth, based on someone’s false testimony to the effect that he saw the new moon of Thul-Hijjah. This Hadeeth indicates that a Muslim is not held accountable for this and should not be depressed because of it. It also denotes that the act of worship is valid and the reward is confirmed, Allah willing.
Sixth: This Hadeeth proves that difficulty is not always a requisite for acts of worship to be rewarded. Allah The Almighty confers upon His servants the favor of rendering a short month equal to a complete month, in terms of reward.
Seventh: This Hadeeth also provides evidence in support of the argument that only a single intention of fasting is sufficient for the whole month of Ramadan, for Allah the Wise made the fasts of the entire month a single act of worship.