Q. I always forget to turn my cell phone off. And my luck always has it that it goes off during my prayers at the musjid. One brother told me that shutting it off in salah is okay because it’s better to be peaceful during salah than playing musical tones. Can I shut it of during salah?

A. Your friend is correct in saying that you can shut your cell phone off, and he is correct that you should be peaceful during your salaah.  But to shut your phone of to be peaceful can be misleading.  Because what he seems to allude to is the notion that you can even use two hands to shut of the phone. Example, place your hand in the pocket, take out the phone with a given hand and shut it off with the other hand.  This would be amal-e-kathir and would break the salaah.  The correct response would be as follows: If a person forgets to turn off the phone prior to salaah, then this phone should be switched off by the usage of just one hand.  A person using both hands will invalidate the salaah.
(Raddul Mukhtar vol.1 Pg.625 as taken from Al Mahmood 10)