Encouragement to fast al-ayyaam al-beed and the month of Sha’baan

Firstly: 

Allaah has forbidden us to speak about Him without knowledge,
and He mentions that alongside shirk and major sins. Allaah says
(interpretation of the meaning): 

“Say (O Muhammad): (But)
the things that my Lord has indeed forbidden are Al-Fawaahish (great evil
sins and every kind of unlawful sexual intercourse) whether committed openly
or secretly, sins (of all kinds), unrighteous oppression, joining partners
(in worship) with Allaah for which He has given no authority, and saying
things about Allaah of which you have no knowledge”

[al-A’raaf 7:33] 

An example of speaking about Allaah with no knowledge is what
is mentioned in the question, that some people say it is a bid’ah (an
innovation) to fast three days in Sha’baan in the manner described in the
question. 

Secondly: it is mustahabb to fast three days each month, and
it is best to fast the ayaam al-beed, which are the 13^th, 14^th
and 15^th of the month. 

It was narrated that Abu Hurayrah (may Allaah be pleased with
him) said: My close friend [the Prophet (peace and blessings of Allaah
be upon him)] advised me to do three things which I will not give up until I
die: fasting three days of each month, praying Duha and going to sleep after
Witr.

Narrated by al-Bukhaari (1124); Muslim (721). 

It was narrated that ‘Abd-Allaah ibn ‘Amr ibn al-‘Aas (may
Allaah be pleased with him) said: The Messenger of Allaah (peace and
blessings of Allaah be upon him) said to me: “It is sufficient for you to
fast three days every month, because for every good deed you will have (the
reward of) ten like it, so that will be like fasting for a lifetime.”

Narrated by al-Bukhaari (1874); Muslim (1159). 

It was narrated that Abu Dharr said: The Messenger of Allaah
(peace and blessings of Allaah be upon him) said to me: “If you fast
any part of the month, then fast the thirteenth, fourteenth and fifteenth.”

Narrated by al-Tirmidhi (761); al-Nasaa’i (2424).

This hadeeth was classed as hasan by al-Tirmidhi, and
al-Albaani agreed with him in Irwa’ al-Ghaleel, 947. 

Shaykh Muhammad ibn
Saalih al-‘Uthaymeen (may Allaah have mercy on him) was asked: 

It was narrated in the hadeeth that the Prophet (peace
and blessings of Allaah be upon him) advised Abu Hurayrah (may Allaah be
pleased with him) to fast three days of each month. When should these fasts
be observed, and should they be one after the other? 

He replied: 

It is permissible to fast these days one after the other or
separately, and they may be at the beginning of the month, or in the middle,
or at the end. The matter is braod in scope, praise be to Allaah, because
the Messenger of Allaah (peace and blessings of Allaah be upon him) did
not state any specific days. ‘Aa’ishah (may Allaah be pleased with her) was
asked: Did the Messenger of Allaah (peace and blessings of Allaah be
upon him) fast three days of each month? She said: Yes. It was asked: In
which part of the month did he fast? She said: He would not bother in which
part of the month he would fast. Narrated by Muslim, (1160). But the 13^th,
14^th and 15^th are better, because these are al-ayyaam
al-beed. 

Majmoo’ Fataawa al-Shaykh Ibn ‘Uthaymeen,
10/ question no. 376. 

Thirdly: Perhaps the one
who told you not to fast on those days in this month (Sha’baan) said that
because he knew that the Prophet (peace and blessings of Allaah be upon
him) forbade fasting in the latter part of Sha’baan. 

In the answer to question no.
49884 we have
explained that this prohibition applies to one who is starting to fast in
the latter part of Sha’baan and does not have a prior habit of fasting. 

But if a person starts to fast in the first half of Sha’baan
and continues to fast in the latter half, or he has a prior habit of
fasting, then there is nothing wrong with him fasting in the latter half of
Sha’baan, such as one who has the habit of fasting three days each month, or
fasting on Mondays and Thursdays. 

Based on this, there is nothing wrong with you fasting three
days in Sha’baan, even if some of those happen to be in the latter half of
the month. 

Fourthly: There is nothing wrong with fasting a great deal in
Sha’baan, indeed that is Sunnah. The Prophet (peace and blessings of
Allaah be upon him) used to fast a great deal during this month. 

It was narrated that ‘Aa’ishah (may Allaah be pleased with
her) said: The Messenger of Allaah (peace and blessings of Allaah be
upon him) used to fast until we thought he would not break his fast, and he
used not to fast until we thought he would not fast. I never saw the
Messenger of Allaah (peace and blessings of Allaah be upon him) fast a
complete month except Ramadaan and I never saw him fast more than in
Sha’baan. 

Narrated by al-Bukhaari, 1868; Muslim, 1165. 

It was narrated from Abu Salamah that ‘Aa’ishah (may Allaah
be pleased with her) said: The Prophet (peace and blessings of Allaah
be upon him) did not fast in any month more than Sha’baan, and he used to
fast all of Sha’baan and he used to say: “Do as much of good deeds as you
can, for Allaah does not get tired (of giving reward) until you get tired.”
And the most beloved of prayers to the Prophet (peace and blessings of
Allaah be upon him) was that in which one persists even if it is little.
When he offered a prayer he would persist in doing so. 

Narrated by al-Bukhaari, 1869; Muslim, 782. 

See also question
49884,
as referred to above. 

And Allaah knows best.