Fathwa - Combining an intention to fasting on Monday andThursday with another fast

Question
Is it permissible to fast the six days of Shawwaal every Monday and
Thursday with both intentions of fasting the six days of Shawwaal
andfasting on Mondays and Thursdays to attain both rewards? What is
the ruleon combining more than one intention in one deed? For example,
is it permissible to fast in Ramadhaan and on Mondays intend the fast
of Ramadhaan along with the Sunnah of fasting on Mondays?
Answer
All perfect praise be to Allaah, The Lord of the worlds. I testify
that there is none worthy of worship except Allaah, and that Muhammad,
is His slave and messenger.
Combining more than one intention in a single deed is what is known
among the people of knowledge as "At-Tashreek". Its ruling is that if
it is done in terms of means or in intersecting matters, it is valid
and the required purpose of both acts of worship is achieved. For
example, if someone performs Ghusl due to Janaabah on Friday for the
sake of Friday and forthe sake of eliminating his Janaabah, then his
Janaabah is eliminated and he attains the reward of having a bath on
Friday. If one of the two acts of worship is not intended but the
other is intended for itself, it is valid to combine them and this
does not detract from theact of worship like performing the prayer of
greeting the Masjid with an obligatory or some other Sunnah prayer.
Greeting the Masjid is notintended for itself but what is intended is
occupying the place with prayer and this happened.
If this is established, thenknow that there is no harm in combining
between fasting on Mondays and Thursdays and any other fasting.
Fasting on Mondays and Thursdays is recommended because they are the
days when deeds are presented to Allaah The Almighty. The Prophet,
liked fasting them for his deeds to be raised while he is fasting.The
Prophet, said: "Deeds are presented (to Allaah) on Monday and Thursday
and I like my deeds to be presented when I am fasting." [As-Suyooti on
the authority of Abu Hurayrah; Al-Albaani: Saheeh]
The questioner should not combine the intention of obligatory fasting
with any voluntary fasting. The intended meaning of fasting on Mondays
and Thursdays is achieved without the need of an intention.
Allaah Knows best.