Criteria For Combining Two Salah
There should be a valid reason ( ‘Usar’/undue difficulty ) for combining and Qasar of Salah, and it is upto the individual to decide whether he or she is faced with such situation or not. Salah cannot be combined without any valid reason. In all ibada rituals the principle is to move down to the closest secondary form ( e.g. combining prayers ) when there’s usr (hardship) ( Further Detail : Discussion 66552 ). A general ruling can’t be made because the situation with one person may justifiably be a hardship, while with another it might be mere inconvenience. Therefore, the final decision on whether or not a particular situation can be justified as hardship rests with the individual. There is a one narration from Ibn-e-Abbas (rta) in Sahih Muslim which does give an impression that this relaxation is not subject to any conditions. But when seen in the framework of Quran and Sunnah, those ahadith are also subject to usar. https://youtu.be/WGROcqL_r4g