Shaban is one of the meritorious months for which we find some particular instructions in the Sunnah of Prophet Muhammad, peace be upon him. It is reported in the authentic ahadith that Prophet Muhammad used to fast most of the month in Shaban. These fasts were not obligatory on him but Shaban is the month immediately preceding the month of Ramadan. Therefore, some preparatory measures are suggested by Prophet Muhammad. Some of these are given below:
1. The blessed companion Anas, may Allah be pleased with him, reports that Prophet Muhammad was asked, "Which fast is the most meritorious after the fasts of Ramadan?" He replied, "Fasts of Shaban in honour of Ramadan." [Tirmidhi]
2. The blessed companion Usama ibn Zaid, may Allah be pleased with him, reports that he asked Prophet Muhammad: "Messenger of Allah,I have seen you fasting in the month of Shaban so frequently that I have never seen you fasting in any other month." Prophet Muhammad replied: "That (Shaban) is a month between Rajab and Ramadan 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." [An-Nasai]
3. Ummul Mumineen Aisha, may Allah be pleased with her, says, "Prophet Muhammad used to fast the whole of Shaban. I said to him, 'Messenger of Allah, is Shaban your most favourite month for fasting?' He said, 'In this month Allah prescribes the list of the persons dying this year. Therefore, I like that my death comes when I am in a state of fasting.'" [Bukhari]
4. In another report Aisha says: "I never saw the Messenger of Allah fast a complete month except for Ramadan, and I have never seen him fast more in a month than he did in Shaban." [Bukhaari, Muslim]
These reports indicate that fasting in the month of Shaban, though not obligatory, is so meritorious that Prophet Muhammad, peace be upon him, did not like to miss it.
But it should be kept in mind that the fasts of Shaban are for those persons only who are capable of keeping them without causing deficiency in the obligatory fasts of Ramadan. Therefore, if one fears that after fasting in Shaban, he will lose strength or freshness for the fasts of Ramadan and will not be able to fast in it with freshness, he should not fast in Shaban, because the fasts of Ramadan, being obligatory, are more important than the optional fasts of Shaban. That is why Prophet Muhammad himself has forbidden the Muslims from fasting one or two days immediately before the commencement of Ramadan. The blessed Companion Abu Hurairah, may Allah be pleased with him, reports Prophet Muhammad to have said, "Do not fast after the first half of the month of Shaban is gone." [Bukhari]
Sha'ban: Merits, Do's, and Dont's - Taqi Usmani