I can not find the misheh berura tht the Rabbi writes that one should was when he uses the bathroom in middle of the night. I did find a m"b that seems to indicate that one need not wash. See m"b siman 1 s"k 2. Can you check the reference and let us know where the other m"b is? TY

ב"ה שלום The Mishna Brura is exactly where I said it is and is also repeated in S"k 33, however I changed the wording. To clarify what I wrote in the previous answer , after using the bathroom he HAS TO wash his hands as one would normally do after the bathroom. However, he does NOT have to do the Netilat Yadayim required upon wakening. In the said Mishna Berura 4:4, I refer to The Chayya Adam (כלל ז סע' ו) which the Mishna Brura quotes who says that if a person wakes up long before Tefilla and knows he will be going to the bathroom again it is best to say the bracha "al netilat Yadayim" upon waking up in the morning before Tefilla (. ( see also the Biur Halacha there "ואפילו". See also הלכות שלמה ב:כג, and (אור לציון ח"ב א, ו The Mishna Berura that you mention refers to a situation when a person plans waking without getting into the detail of if he has to use the bathroom. All the best