Fathwa - Ruling on fasting optional days before making up the obligatory fast

Question
i have outstanding days from remmadan that i didn't fast and i made an
intention to fast ashoura,but while i was fasting i found out that it
is not permissible to fast ashoura while you have outstanding days to
fast from remmedan. can i make my current fasting from intention of
ashura to intention of remmendan on half day.
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
MuhammadisHis slave and Messenger.
Dear sister, you cannot change your intention of fasting from optional
fasting to making up a missed fast, because making up a missed fast
has to be designated by having the intention in the night before the
true dawn.
The Fiqh Encyclopedia reads:"Having an overnight intention: this is a
condition regarding the obligatory fasts according to the Maaliki,
Shaafi'i and Hanbali Schools of jurisprudence. Having an overnight
intention means initiating the intention by night between sunset and
dawn... The Hanafi School of jurisprudence conditioned having an
overnight intention for fasting expiations, absolute )unconditional(
vows, and making up for missed fasts in Ramadhaan."
Therefore, it is not acceptable that you intend making up for thefast
of Ramadhaan during the day, whether you are fasting for 'Aashooraa'
or observing any other fast.
However, we hope that itis permissible for you to fast 'Aashooraa'
before making up for missed days in Ramadhaan though it is better to
make up the missed fast first. But if you fast, your fasting is valid
– Allaah willing – according to theview of the majority of the
scholars.
The Fiqh Encyclopedia reads:"The scholars differed in opinion
concerning the ruling of optional fast before making up for missed
days in Ramadhaan: The Hanafi School of jurisprudence is of the view
that it is permissibleto fast optional fasting before making up for
missed days in Ramadhaan without any dislikeability, as it is not an
obligation to immediately make up themissed fast. However, theMaaliki
and Shaafi'i Schools of jurisprudence are of the view that it is
permissible to fast optional fasting before making up for missed days
but this is disliked, as in this case, one delaysthe
obligation.Ad-Dusooqi)from the Maaliki School of jurisprudence( said:
It is disliked to observe optional fasting while one has an obligatory
fast, like vowed fasts, missed days )in Ramadhaan( and expiations;
whether the optional fast that one observed before making up an
obligatory fast is not a confirmed fast or is a confirmed fast, like
'Aashooraa' and the 9th of Thul-Hijjah )i.e. the day of 'Arafah(
accordingto the preponderant opinion of the scholars. The Hanbali
School of jurisprudence is of the view that it is forbidden to observe
optional fast before making up for missed days in Ramadhaan, and the
optional fasting, in this case, is not valid even if there is enough
time for making up the fast…."
Allaah Knows best.