Is it permissible, even after finding out that a hadeeth is
da’eef (weak), to follow it, by way of doing righteous deeds?
The hadeeth says: “When it is halfway through Sha’baan, spend
that night in prayer and fast on that day.” The fast is
observed as a voluntary act of devotion to Allaah, as is
spending that night in prayer (qiyaam al-layl).


Praise be to Allaah.

Firstly:

What is narrated concerning the
virtue of praying, fasting and worshipping on the fifteenth
of Sha’baan (al-nusf min Sha’baan) does not come under the
heading of da’eef (weak), rather it comes under the heading
of mawdoo’ (fabricated) and baatil (false). So it is not
permissible to follow it or to act upon it, whether that is
in doing righteous deeds or otherwise.

A number of scholars ruled that
the reports concerning that were false, such as Ibn al-Jawzi
in his book al-Mawdoo’aat, 2/440-445; Ibn Qayyim
al-Jawziyyah in al-Manaar al-Muneef, no. 174- 177; Abu
Shaamah al-Shaafa’i in al-Baa’ith ‘ala Inkaar al-Bida’
wa’l-Hawaadith, 124-137; al-‘Iraaqi in Takhreej Ihyaa’
‘Uloom il-Deen, no. 582. Shaykh al-Islam [Ibn Taymiyah]
narrated that there was consensus on the fact that they are
false, in Majmoo’ al-Fataawa, 28/138.

Shaykh Ibn Baaz (may Allaah have
mercy on him) said in Hukm al-Ihtifaal bi Laylat al-Nusf
min Sha’baan (Ruling on celebrating the fifteenth of
Sha’baan):

Celebrating the night of the
fifteenth of Sha’baan (Laylat al-Nusf min Sha’baan) by
praying etc, or singling out this day for fasting, is a
reprehensible bid’ah (innovation) according to the majority
of scholars, and there is no basis for this in
sharee’ah.

And he (may Allaah have mercy on
him) said:

There is no saheeh hadeeth
concerning the night of the fifteenth of Sha’baan (Laylat
al-Nusf min Sha’baan). All the ahaadeeth that have been
narrated concerning that are mawdoo’ (fabricated) and da’eef
(weak), and have no basis. There is nothing special about
this night, and no recitation of Qur’aan or prayer, whether
alone or in congregation, is specified for this night. What
some of the scholars have said about it being special is a
weak opinion. It is not permissible to single it out for any
special actions. This is the correct view. And Allaah is the
Source of strength.

Fataawa
Islamiyyah,
4/511.

See also question no. 8907.

Secondly:

Even if we assume that the
hadeeth is da’eef (weak) and not mawdoo’ (fabricated), the
correct scholarly view is that weak ahaadeeth should not be
followed at all, even if they speak of righteous deeds or of
targheeb and tarheeb (promises and warnings). The saheeh
reports are sufficient and the Muslim has no need to follow
the da’eef reports. Nothing is known in Islam to suggest that
this night or day is special, either from the Prophet
(peace and blessings
of Allaah be upon him) or from his companions.

The scholar Ahmad Shaakir said:
There is no difference between rulings or righteous deeds; we
do not take any of them from da’eef reports, rather no one
hast he right to use any report as evidence unless it is
proven to be soundly narrated from the Messenger of Allaah
(peace and blessings
of Allaah be upon him) in a saheeh or hasan hadeeth.

Al-Baa’ith
al-Hatheeth,
1/278.

For more information, see:
al-Qawl al-Muneef fi Hukm al-‘Aml bi’l-Hadeeth
al-Da’eef.

See also the answer to question
no. 44877.

And Allaah knows best.