Shaikh Muhammad bin Hizaam (may Allah preserve him) said in his book Fathul-‘Allaam (2/725-726),
“The ruling on fasting Saturday alone
The mathhab of the Shafi’yyah and the Hanaabilah is that it is disliked to fast Saturday voluntarily due to the Hadith of as-Samaa (may Allah be pleased with her) that preceded [the Hadith is the following:
The Prophet said (ﷺ):
لاَ تَصُومُوا يَوْمَ السَّبْتِ إِلاَّ فِيمَا افْتُرِضَ عَلَيْكُمْ وَإِنْ لَمْ يَجِدْ أَحَدُكُمْ إِلاَّ لِحَاءَ عِنَبَةٍ أَوْ عُودَ شَجَرَةٍ فَلْيَمْضُغْهُ
Do not fast on Saturday except what has been made obligatory on you; and if one of you can get nothing but a grape skin or a piece of wood from a tree, he should chew it [Graded Saheeh by Imam al-Albani in Saheeh Sunan Abi Dawood (no. 2421) and by Shaikh Muhammad bin Hizaam in his Tahqiq of Bulugh al-Maram (no. 675)
at-Tirmidhi, Ibn Khuzaymah, Ibn Hibban, and al-Bayhaqi chose this as the preponderate view and Ibn al-Qayyim inclined to its dislike.
at-Tirmidhi (may Allah have mercy upon him) said: ‘the meaning of the prohibition is for a person specifying fasting on this day because the Jews venerate this day’. End translation.
Ibn Khuzaimah (may Allah have mercy upon him) said, ‘Chapter: The prohibition of fasting on Saturday voluntarily if he fasts that day alone’. He said, ‘I consider the prohibition is for a person fasting this day when the Jews venerate it and for a person taking this day as an Eid instead of Friday’. End translation.
Al-Bayhaqi (may Allah have mercy upon him) (4/303) said, ‘It is as if he (ﷺ) intends the prohibition for specifying this day with fast by way of veneration’ End translation.
Ibn Hibban (may Allah have mercy upon him) said, ‘Chapter: The Rebuke of Fasting Saturday Alone
Ibn Muflih (may Allah have mercy upon him) said in al-Furoo’: “Our Shaikh, Shaikhul-Islaam Ibn Taymiyyah, chose the view that it is not disliked and this is the opinion of the majority of the scholars. This is what al-Athram understood from his (Imam Ahmad’s) narration. If he (ﷺ) intended for it to be prohibited to fast Saturday alone, he would not have exempted fasting the obligatory fast alone on this day. However, the Hadith is Shaath or abrogated. This is the way of the earlier Companions of Imam Ahmad who accompanied him like al-Athram and Abu Dawud”‘. End translation.
I say that those who say that it is not disliked use as evidence the Hadith of Umm Salmah (may Allah be pleased with her) mentioned in this book. It is Daif as preceded.
They also use as proof the hadith
of Abu Hurairah (may Allah be pleased with him) in the Saheehayn,
Do not fast on the day of Friday except if one of you fasts a day before or a day after
And the Hadith
of Juwayriah (may Allah be pleased with her) in al-Bukhari (no. 1986) that
the Prophet (ﷺ) entered upon her on the day of Friday while she was fasting. He said, ‘Did you fast yesterday?’ She said, ‘No’. He said, ‘Will you fast tomorrow?’ She said, ‘No’. So he (ﷺ) said, ‘So break your fast’
The response to these Ahaadith is that it is not reported in relation to fasting Saturday alone, but fasting it with Friday.
An-Nawawi (may Allah have mercy upon him) said, ‘As for the remaining Ahaadith which we mentioned fasting Saturday, then all of them are reported in relation to fasting Saturday with Friday and Sunday. So it does not oppose what our Companions (i.e. the Shafi’yyah) say about the dislike of fasting Saturday alone’. End translation.
I say [that] the speech of at-Tirmidhi, Ibn Khuzaimah, Ibn Hibban, al-Bayhaqi has preceded, that the intent of the prohibition is in regards to singling out Saturday alone and specifying it by fasting it out of veneration. This is the correct opinion and Allah knows best. See al-Majmoo’ (6/392) Maktabah al-Irshaad, al-Insaaf (3/313-314), Zaad al-Ma’aad (2/79), and al-Faroo’ (3/123)” End translation.
And Allah knows best
Faisal bin Abdul Qaadir bin Hassan