Reference: https://binothaimeen.net/content/13250
Question: When is Ṣalāh to be combined, and when can it be shortened? [1]
Response: Qaṣr (shortening Ṣalāh) only has one cause: travelling. Whenever a person undertakes a journey, he shortens Ṣalāh, regardless of whether his period of travelling is long or short. However, if he prays behind an Imām, he must pray Ṣalāh completely (i.e. without shortening it). If he is in a town, he must attend the Jamā’ah (congregational Ṣalāh) and pray completely.
As for Jam’ (combining Ṣalāh), its cause is a difficulty. Whenever there is a difficulty, it is permitted to combine Ṣalāh. This applies to any type of difficulty, to the extent that the scholars – may Allāh have mercy upon them – said: it is permitted for a pregnant woman to combine Ṣalāh if it is too difficult for her to pray each Ṣalāh in its time. Similarly, a woman who is breastfeeding, if her baby urinates upon her and it is too difficult for her to wash her clothes for every Ṣalāh, [she can combine]. And other similar situations.
In conclusion, combining the Prayers has only one cause: difficulty, although this difficulty may take various forms. As for shortening Ṣalāh, it is only permitted during a journey.
If a person was ill in the hospital, he can combine Prayers if it is too difficult for him to pray each Ṣalāh in its time, however, he cannot shorten the Prayers because he is resident in his town. However, if he was in a hospital in a different town, it would be permitted for him to combine and shorten – as he is travelling. Yes.
Footnotes
[1] The meaning of al-Jam’ (combining) is for a person to combine Dhuhr and ‘Asr, or Maghrib and ‘Isha. This combining can be done by praying them both at the time of the earlier Salah, or later Salah. No other sets of Salah can be combined.
Qasr is to shorten a 4 Raka’ah Salah and pray it as 2 Raka’ah.
متى يجوز الجمع والقصر للصلاة؟
المرجع: فتاوى نور على الدرب>الشريط رقم 372
السؤال: متى يكون الجمع في الصلاة، ومتى يكون القصر مأجورين؟
الجواب: القصر ليس له إلا سبب واحد وهو السفر. فمتى كان الإنسان مسافراً فإنه يقصر سواء طالت المدة أم قصرت ، لكن إذا صلى مع إمام يتم وجب عليه الإتمام. وإذا كان في بلد وجب عليه أن يحضر الجماعة ويتم.
وأما الجمع فسببه المشقة ، فمتى حصلت مشقة جاز الجمع في أي سبب من الأسباب ، حتى إن العلماء رحمهم الله قالوا: إنه يجوز الجمع للحامل إذا شق عليها أن تصلي كل صلاة في وقتها ، وللمرضع إذا كان صبيها يبول عليها ويشق عليها غسل ثيابها لكل صلاة وما أشبه ذلك.
فالحاصل أن الجمع له سبب واحد -أي نعم- وهو المشقة ، لكن صوره كثيرة وأما القصر فليس له إلا السفر فقط.
لو فرض أن إنساناً مريضاً في المستشفى فله أن يجمع بين الصلاتين إذا شق عليه إفراد كل صلاة في وقتها، ولكنه لا يقصر لأنه في بلده، ولو كان في مستشفى في بلد آخر جاز له أن يجمع ويقصر لأنه مسافر. نعم.
