Sha’baan is the eighth month of the Islamic calendar, falling between the holy month of Rajab and the glorious month of Ramadhan. The word “Sha’baan” means to spread or distribute. This month was so called because during this time the people of Arabia dispersed in search of water or set out on military expeditions after the holy month of Rajab had ended.
Sha’baan is one of the meritorious months for which we find particular instructions in the Sunnah of Prophet Muhammad ﷺ. It is reported in the authentic Ahaadith that Nabi ﷺ used to fast most of the month in Sha’baan. These fasts were not obligatory on him but Sha’baan is the month immediately preceding the month of Ramadhan. Therefore, Nabi ﷺ began his preparations of fasting right from the month of Sha`baan.

The blessed companion Anas, Radi-Allahu anhu, reports that Nabi ﷺ was asked, “Which fast is the most meritorious after the fasts of Ramadhan?” He replied, “Fasts of Sha`baan in honour of Ramadhan.”
قَالَ حَدَّثَنِي أُسَامَةُ بْنُ زَيْدٍ، قَالَ قُلْتُ يَا رَسُولَ اللَّهِ لَمْ أَرَكَ تَصُومُ شَهْرًا مِنَ الشُّهُورِ مَا تَصُومُ مِنْ شَعْبَانَ . قَالَ ” ذَلِكَ شَهْرٌ يَغْفُلُ النَّاسُ عَنْهُ بَيْنَ رَجَبٍ وَرَمَضَانَ وَهُوَ شَهْرٌ تُرْفَعُ فِيهِ الأَعْمَالُ إِلَى رَبِّ الْعَالَمِينَ فَأُحِبُّ أَنْ يُرْفَعَ عَمَلِي وَأَنَا صَائِمٌ ”
The blessed companion Usama ibn Zaid RA, reports that he asked Nabi ﷺ “Messenger of Allah, I have seen you fasting in the month of Sha’ban so frequently that I have never seen you fasting in any other month.” Allah`s Messenger ﷺ replied: “That (Sha’ban) is a month between Rajab and Ramadhan which is neglected by many people. And it is a month in which an account of the deeds (of human beings) is presented before the Lord of the universe, so, I wish that my deeds be presented at a time when I am in a state of fasting.” [Sunan an-Nasa’i 2357]

Ummul Mu’mineen ‘Aishah RA says:
عَنْ عَائِشَةَ، قَالَتْ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَصُومُ حَتَّى نَقُولَ مَا يُفْطِرُ وَيُفْطِرُ حَتَّى نَقُولَ مَا يَصُومُ وَمَا رَأَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم فِي شَهْرٍ أَكْثَرَ صِيَامًا مِنْهُ فِي شَعْبَانَ .
“Nabi ﷺ would sometimes begin to fast continuously until we thought he would not stop fasting, and sometimes he used to stop fasting until we thought he would never fast. I never saw the Messenger of Allah fasting a complete month, except the month of Ramadan, and I have never seen him fasting in a month more frequently than he did in Sha’ban.” [Sunan an-Nasa’i 2351]

These reports indicate that fasting in the month of Sha’baan, though not obligatory, is so meritorious that Prophet Muhammad ﷺ did not like to miss it.

But it should be kept in mind that the fasts of Sha’baan are for those persons only who are capable of keeping them without causing deficiency in the obligatory fasts of Ramadhan.

Therefore, if one fears that after fasting in Sha’baan, he will lose strength or freshness for the fasts of Ramadhan and will not be able to fast in it with freshness, he should not fast in Sha’baan, because the fasts of Ramadhan, being obligatory, are more important than the optional fasts of Sha’baan. That is why Nabi ﷺ himself has forbidden the Muslims from fasting one or two days immediately before the commencement of Ramadhan. The blessed Companion Abu Hurairah RA, reports Prophet Muhammad ﷺ to have said, “Do not fast after the first half of the month of Sha’baan is gone.”

The essence of the above-quoted hadith is that Nabi ﷺ himself used to fast most of the month of Sha’baan, because he had no fear of developing weakness or weariness before the commencement of Ramadhan. As for others, he ordered them not to fast after the 15th of Sha’baan for the fear that they would lose their strength and freshness before Ramadhan starts, and would not be able to welcome the month of Ramadhan with enthusiasm.