The fast that is intended for its own sake includes the Ramadan fast, making up missed Ramadan fasts, fasting in fulfilment of a vow, and fasting on special days, such as the days of `Arafah and `Ashura’, and fasting on Mondays. With regard to that which is not intended for its own sake, this refers to cases where the aim is to observe a type of recommended fast, without needing to observe the fast on any particular day, such as fasting three days of every month. In that case, it is permissible to form the intention that you want to combine fasting the day of `Arafah or fasting on a Monday with fasting one of the three days of every month.

It is permissible to observe i‘tikaaf in more than one mosque, although it is better to observe i‘tikaaf in one mosque; it is permissible to go out to another mosque if one stipulates that when beginning i‘tikaaf. However, it should be noted that the one who goes out of the mosque where he began his i‘tikaaf to observe i‘tikaaf in another mosque, for one or two nights, is missing out on doing i‘tikaaf for all ten nights, according to what is proven in the Sunnah. That is because his i‘tikaaf in the first mosque ends when he leaves the mosque, and his i‘tikaaf in the second mosque does not begin until he actually enters the mosque. For more details, please see the long answer.