Is it permissible to greet a person who is praying?
Machine translationRead the Arabic original
The questioner : Do you greet a person who is praying?
The Shaykh : There is nothing wrong with greeting him, but if you fear that you will disturb his prayer, do not greet him.
The questioner : And if you speak to him, how does the one who is praying respond?
The Shaykh : He responds with a gesture.
The questioner : Now, if the one you greeted while he was praying forgot and said, "Peace be upon you," is his prayer invalidated? He said, "Peace be upon you."
The Shaykh : Yes, it is not invalidated because he was forgetful, and the forgetful person who speaks during prayer owes nothing, by the saying of Allah the Exalted:[Al-Baqarah 2:286].
The Shaykh : There is nothing wrong with greeting him, but if you fear that you will disturb his prayer, do not greet him.
The questioner : And if you speak to him, how does the one who is praying respond?
The Shaykh : He responds with a gesture.
The questioner : Now, if the one you greeted while he was praying forgot and said, "Peace be upon you," is his prayer invalidated? He said, "Peace be upon you."
The Shaykh : Yes, it is not invalidated because he was forgetful, and the forgetful person who speaks during prayer owes nothing, by the saying of Allah the Exalted:
Our Lord, do not impose blame upon us if we have forgotten or erred.
رَبَّنَا لَا تُؤَاخِذْنَا إِن نَّسِينَا أَوْ أَخْطَأْنَا
Source
قناة «فضيلة الشيخ محمد بن صالح العثيمين»، 32 - 64 هل يجوز السلام على المصلي؟ طالب العلم والمجتمع - ابن عثيمين — youtube.com
The Arabic text is a machine transcription of the audio recording.