Question
What is the ruling for someone who mistakenly concluded the prayer with Salam and has not finished the prayer yet?
Answer
If the Salam was done mistakenly, it does not invalidate the prayer because Salam is considered a remembrance. However, if the Salam was done intentionally, it invalidates the prayer. In cases of non-intentional Salam, it is considered a remembrance, while in cases of intentional Salam, it is considered speech. See: Al-Bahr 2: 8-9, Fath Bab Al-Inayah 1: 301, Radd Al-Muhtar 1: 414.