Ibn Uthaimeen (rahimhaullaah) on Fasting on a Saturday if is the Day of ‘Aashoorah
The Messenger of Allaah (salallaahu ‘alaihi wassallam) said: “Do not fast on Saturday except that which is an obligation upon you. And if one of you does not find except a grape peel or a tree’s twig, then let him chew it.” (At-Tirmidhee, 744. Abu Dawood, 2421. Ibn Maajah, 1726)
Abu Dawood (rahimahullaah) said: “This hadeeth has been abrogated.”
Imaam at-Tirmidhee said: “This hadeeth is Hasan. The meaning of dislike here applies to the man who singles out Saturday with fasting due to the fact that the Jews revere this day.” He also said: “The majority of Scholars see that it is not disliked.”
Al-Athram said: “The proof utilised by Abu Abdillaah (Ahmad bin Hanbal) in allowing fasting on a Saturday is that all of the ahaadeeth oppose the hadeeth of Busr (i.e. the hadeeth above) – and from them is the hadeeth of Umm Salamah (radhi Allaahu ‘anhaa) when she was asked: On which days did the Prophet (salallaahu ‘alaihi wassallam) predominantly fast? So she responded: Saturday and Sunday. (Ahmad, 6/324)”
Ibn Uthaimeen (rahimahullaah) stated: “It is known that fasting on a Saturday has different scenarios:
The first scenario: That [the fast] is obligatory like that of Ramadaan, so he fasts – or it is making up of an obligatory fast or an expiation, or in replacement for the one who did not sacrifice whilst at Hajj at-Tamattu’. So in this there is no harm, so long as he does not single it out with fasting believing it to be [more] virtuous.
The second scenario: That he fasts the day before it, Friday, then there is no harm in that. This is because the Prophet (salallaahu ‘alaihi wassallam) to one of the Mothers of the Believers who fasted on a Firday: “Did you fast yesterday?” She said: “No.” He said: “Are you going to fast tomorrow (i.e. Saturday)?” She said: “No.” So he said: “Then break your fast.” (Bukhaaree, 1986) So his saying, “Are you going to fast tomorrow?” proves the permissibility of fasting Saturday along with Friday.
The third scenario: That the legislated fasts happen to coincide with Saturday, such as the middle of month recommended fasts, or the day of ‘Arafah, or the day of ‘Aashooraa, or the six days of Shawwaal for the one who fasted Ramadaan, or the nine days of Dhul-Hijjah, then there is no harm in fasting because one is not fasting because it is a Saturday, rather he fasts because it is legislated to fast on these occasions.
The fourth scenario: That fasting on a Saturday happens to coincide with one’s habit such as the one who fasts one day and leaves off fasting the next day [and so on] – so the day he is fasting happens to coincide with a Saturday, in this case there is no harm. [This is] like the the saying of the Prophet (salallaahu alaihi wassallam) in forbidding fasting a day or two days just prior to Ramadaan except for the one who is in the habit of fasting (Bukhaaree, 1914). So here there is no forbiddance, so this case is similar.
The fifth scenario: That a person singles out Saturday alone for the optional fast, then this is forbidden, if it is assumed that the hadeeth of forbiddance of fasting on a Saturday is authentic.” ( See Majmoo’ Fatawa Ibn al-Uthaimeen, Vol. 20, p. 57-58)
Ibn Uthaimeen also stated: “It is established from the Sunnah of the Messenger (salallaahu ‘alaihi wassallam) in speech and action that fasting on a Saturday is not forbidden. The Scholars differ with respect to the hadeeth that forbids fasting on Saturday as to whether it is acted upon. From them are those who say that it is not to be acted upon at all, and there is no harm in fasting on a Saturday, whether it be on its own or not on its own because the hadeeth is not authentic. And a regulation cannot be established from a hadeeth which is not authentic.
From them are those who have said the hadeeth is Saheeh or Hasan, and they said: The reconciliation between this hadeeth [that forbids fasting on a Saturday] and the other ahaadeeth [that allow fasting on a Saturday], is that it is forbidden to single out Saturday on its own – meaning that Saturday is singled out without Friday or Sunday. This was the position of Imaam Ahmad (rahimahullaah), wherein he said: “If one fasts alongside Saturday another day, then there is no harm, such as fasting with it Friday or Sunday… Indeed I have heard that some of the people fast on the ninth and tenth of Muharram (‘Aashooraa), and one the days happens to be a Saturday, and some of the brothers forbid them and command them to break the fast – this is wrong and it is upon this brother to ask before issuing a verdict without knowledge.” (Majmoo’ Fatawa Ibn al-Uthaimeen, vol. 20, p. 37)