ANSWER:

Fard prayers must not be offered while sitting except when a person is unable to stand! Voluntary prayers are permissible to be offered sitting down but the reward is half that of standing up. 

Can fard salah be performed sitting down without any reason?

Prayer | March 26, 2018 7:51 am
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After finishing salah, as I stood up, I realized that the person just behind me was performing salat. Can I move at this time or I will have to wait till he finishes salat?
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Sheikh, is there a ruling to say the surahs in order in salah? E.g. if in the first rakah we say surah Falaq, can we not say surah Ikhlas in the subsequent rakah or we necessarily have to say surah Nas?