It seems to me you refer to the sahih hadith:
The Prophet (ﷺ) was more shy than a virgin in her separate room. And if he saw a thing which he disliked, we would recognize that (feeling) in his face. (Sahih al-Bukhari and Sahih Muslim)
Mullah 'Ali al-Qari commented the statement (if he saw a thing which he disliked) in his Mirqat al-Mafateeh sahrh Mishkat al-Massabih مرقاة المفاتيح شرح مشكاة المصابيح -see here in Arabic- as follows:
In the following I'm translating from Arabic as these are my own translations take them with the necessary.
فإذا رأى شيئا يكرهه ) أي : من جهة الطبع أو من طريق الشرع
This means either due to his moral constitution or due to the rulings of shari'a.
He then goes on:
( عرفناه في وجهه ) . أي من أثر التغير فأزلناه ، فإنه ما كان يعاين أحدا بخصوصه في أمر الكراهة دون الحرمة . قال النووي : معناه أنه - صلى الله عليه وسلم - لم يتكلم بالشيء الذي يكره لحيائه بل يتغير وجهه ، فنفهم كراهيته
(we would recognize that in his face) from the clear signs of change so that we would change/remove it, as he was not used to survey a single person in case of dislike which doesn't reach haram. An-Nawawi said: it means that he -Allahs prayers and blessings be upon him- was not used to speak about something he disliked due to his shyness (haya') but his face changed so that people understood or concluded his dislike.