When Sha’baan is half over
The Messenger of Allah (sal Allahu alaihi wa sallam) said, “When Sha’baan is half over, do not fast.”
[Sunan Abu Dawood and al-Tirmidhi and others - Classed as Sahih by Sh al-Albaani]
This above Hadith indicates that it is not allowed to fast after halfway through Sha’baan, i.e., starting from the sixteenth day of the month.
But there are reports that indicate that it is permissible to fast at this time.
1. The Prophet (sal Allahu alaihi wa sallam) said: “Do not anticipate Ramadan by fasting one or two days before it begins, but if a man habitually fasts, then let him fast.” [Sahih Al-Bukhari and Muslim]
This indicates that fasting after halfway through Sha’baan is permissible for someone who has the habit of fasting, such as a man who regularly fasts on Mondays and Thursdays, or who fasts alternate days, and the like.
2. ‘Aa’ishah (radi Allahu anha) said: “The Messenger of Allah (sal Allahu alaihi wa sallam) used to fast all of Sha’baan, he used to fast Sha’baan except a few days.” [Sahih Muslim]
Imam Al-Nawawi (may Allah have mercy upon him) said: In the words, “He used to fast all of Sha’baan, he used to fast Sha’baan except a few days” the second phrase explains the first, and indicates that the word “all” means “most of”.
This hadith indicates that it is permissible to fast after halfway through Sha’baan, but only for those who are continuing after fasting before halfway through the month.
According to most of the scholars, the prohibition here means that it is haram.
Other Scholars suggested that the prohibition here is to be understood as meaning that it is makrooh, not haraam.
Imam Al-Nawawi (may Allah have mercy upon him) said in Riyaadh al-Saaliheen:
“Chapter on the prohibition on anticipating Ramadaan by fasting after halfway through Sha’baan, except for one who is continuing after fasting before halfway through the month or who has a regular pattern of fasting such as fasting on Mondays and Thursdays”.
Ibn al-Qayyim (may Allah have mercy upon him) said in Tahdheeb al-Sunan,
With regard to those who think that there is a contradiction between this Hadith and the ahadith which speak of fasting in Sha’baan, there is no contradiction. Those ahadith speak of fasting half of it along with the previous half, and of habitual fasting during the second half of the month, whereas the hadith of al-‘Ala’ (the Hadith in discussion) speaks of the prohibition on fasting deliberately only after the month is halfway over, not about fasts that a person observes regularly or that are a continuation after fasting during the first part of the month.
It is not allowed to fast during the second half of Sha’baan, and that is either mukroo (disliked) or haram (prohibited), except for the one who has the habit of fasting regularly or who is continuing after fasting during the first half of Sha’baan.
The reason for this prohibition is that continually fasting may make a person too weak to fast in Ramadan.
If it is said that if he fasts from the beginning of the month he will become even weaker, the response is that whoever fasts from the beginning of Sha’baan will have gotten used to fasting so it will be less difficult for him to fast.
Al-Qaari (may Allah have mercy upon him) said: The prohibition here means that it is disliked, as a mercy to this ummah lest they become too weak to fulfil their duty of fasting during Ramadan in an energetic fashion. But those who fast all of Sha’baan will become used to fasting so it will not be difficult for them.
And Allah knows best!