Commentary for Berakhot 113:14

הנפנה בחלום סימן יפה לו שנאמר (ישעיהו נא, יד) מהר צועה להפתח וה"מ דלא קנח

Who dreams that he is performing the functions of nature, it is a good omen for him ; as it is said, "He that is bent down shall speedily be loosed" (ls li. 14). But that only applies if he does not [dream of] wiping himself.

Abraham Cohen Footnotes to the English Translation of Masechet Berakhot