Is Fasting Most of Sha’ban Recommended?
Question

Is it Sunnah to fast the entire month of Sha’ban?
Praise be to Allah.Is it sunnah to fast the whole month of Sha’ban?
It is mustahabb to fast a great deal in the month of Sha’ban . 
The Prophet Muhammad (peace and blessings of Allaah be upon him) used to fast the whole of Sha’ban. 
Ahmad (26022), Abu Dawud (2336), al-Nasai (2175) and Ibn Majah (1648) narrated that Umm Salamah (may Allah be pleased with her) said: “I never saw the Messenger of Allah (peace and blessings of Allah be upon him) fast two consecutive months apart from the fact that he used to join Sha’ban and Ramadan.” 
According to a version narrated by Abu Dawud: “The Prophet (peace and blessings of Allah be upon him) never used to fast any complete month in the year, apart from Sha’ban, which he used to join to Ramadan .” Classed as sahih by al-Albani in Sahih Abi Dawud, 2048. 
The apparent meaning of this hadith is that the Prophet (peace and blessings of Allah be upon him) used to fast the entire month of Sha’ban. 
But it was also narrated that the Prophet (peace and blessings of Allah be upon him) used to fast all of Sha’ban apart from a few days . 
Muslim (1156) narrated that Abu Salamah said: “I asked ‘Aishah (may Allah be pleased with her) about the fasting of the Messenger of Allah (peace and blessings of Allah be upon him), and she said: ‘He used to fast until we thought that he would always fast, then he would not fast until we thought that he would always not fast, but I never saw him fast in any month more than he fasted in Sha’ban. He used to fast all of Sha’ban, and he used to fast all of Sha’ban apart from a few days.’”
Reconciling between the hadiths about the Prophet’s fasting in Sha’ban
The scholars differed as to the way of reconciling between these hadiths. 
Some of them said that this had to do with differences of time – in some years the Prophet (peace and blessings of Allah be upon him) fasted all of Sha’ban, and in other years he fasted all of that month apart from a few days. This was the view favoured by Shaykh Ibn Baz (may Allah have mercy on him). See Majmu’ Fatawa al-Shaykh Ibn Baz, 15/416. 
Others said that the Prophet (peace and blessings of Allah be upon him) never fasted any month in full apart from Ramadan, and they interpreted the hadith of Umm Salamah as meaning that he fasted all of Sha’ban apart from a few days. They said that this is possible from a linguistic point of view, that if a man fasts for most of a month it may be said that he fasted the whole month. 
Al-Hafiz said: 
“The hadith of ‘Aishah explains what was said in the hadith of Umm Salamah, which says that he did not fast any month of the year in full apart from Sha’ban which he used to join to Ramadan; this means that he used to fast most of it. Al-Tirmidhi narrated that Ibn al-Mubarak said: It is possible in the language of the Arabs, if a person fasts most of a month, to say that he fasted the whole month…” 
Al-Tibi said: “It may be interpreted as meaning that he used to fast all of Sha’ban sometimes and most of Sha’ban at other times, lest people think that it is obligatory to fast the entire month, like Ramadan.” 
Then al-Hafiz said: The former is the correct view.”
In other words, that the Prophet (peace and blessings of Allah be upon him) did not fast all of Sha’ban. He quoted as evidence for that the report narrated by Muslim (746) from ‘Aishah (may Allaah be pleased with her) who said: “I do not know that the Prophet of Allah (peace and blessings of Allah be upon him) recited the entire Quran in one night, or spent an entire night in prayer until dawn, or fasted an entire month apart from Ramadan.” 
And he quoted the report narrated by al-Bukhari (1971) and Muslim (1157) from Ibn ‘Abbas (may Allah be pleased with him) who said: “The Prophet (peace and blessings of Allah be upon him) never fasted any month in full apart from Ramadan.” 
Al-Sindi said in his commentary on the hadith of Umm Salamah: 
“He joined Sha’ban to Ramadan” means that he fasted them both together. The apparent meaning is that he fasted all of Sha’ban… but there are reports which indicate something different. Hence it is to be understood as meaning that he used to fast most of it, so it was as if he fasted all of it and joined it to Ramadan.” 
Why is it recommended to fast a great deal during Sha’ban?
If it is asked, what is the reason for fasting a great deal during Sha’ban ? The answer is: 
Al-Hafiz said: 
“The reason is explained in the report narrated by al-Nasai and Abu Dawud, and classed as sahih by Ibn Khuzaymah, according to which Usamah ibn Zayd said: “I said, ‘O Messenger of Allah, I do not see you fasting in any month more than in Sha’ban.’ He said, ‘That is a month concerning which many people are heedless, between Rajab and Ramadan. It is the month is which people’s deeds are taken up to the Lord of the Worlds, and I would like my deeds to be taken up whilst I am fasting.’” (Classed as hasan by al-Albani in Sahih al-Nasai, 2221)
And Allah knows best.