The Days on which Fasting is disliked

1) the one performing hajj fasting on the day of 'arafah.

the messenger of allah (peace be upon him) said:

((the day of 'arafah and the day of nahr and the days of tashreeq are the (days of) 'eed for the muslims, and they are the days for eating and drinking)),

[saheeh, transmitted by abu daawood]

2) singling the day of jumu'ah (friday) out for fasting.

the messenger of allah (peace be upon him) said:

((do not fast the day of jumu'ah (friday), unless you fast a day before it (also) or the day after it (also))),

[the authenticity of this narration has been agreed upon by al-bukhaaree and muslim]

3) singling the day of saturday out for fasting.

the messenger of allah (peace be upon him) said:

((do not fast the day of saturday, unless it is an obligatory fast upon you, and even if any of you were to find only grape skin or a wooden stick, then chew it)),

[saheeh, transmitted by ahmad]

4) fasting the entire year without missing a day.

the messenger of allah (peace be upon him) said:

((whoever fasts the (entire) year, then neither has he fasted nor has he not fasted)),

[saheeh, transmitted by an-nasaa.ee]

5) fasting two days or more simultaneously without breaking the fast after the first day. this is what is called "al-wisaal".

the messenger of allah (peace be upon him) said:

((beware of al-wisaal)), i.e. do not fast the fast of al-wisaal,

[the authenticity of this narration has been agreed upon by al-bukhaaree and muslim] 

and the messenger of allah (peace be upon him) also said:

((do not fast continuously. whoever amongst you wishes to fast continuously then do so for a day (only))),

[transmitted by al-bukhaaree] 

6) fasting the day of doubt, which is the 30th day of sha'baan.

'ammaar ibn yaasir (may allah be pleased with him) said:

((whoever fasts the day on which there is doubt (as to whether ramadan has begun or not), then he has gone against (the guidance of) abul-qaasim (muhammad (peace be upon him))),

[transmitted by abu daawood]

and the messenger of allah (peace be upon him) said:

((do not preceed ramadan by fasting a day or two days before it, except for the person who regularly fasts)),

[transmitted by muslim]