There was once a gathering in the memory of a late tzadik ["hilula"] attended by Rav Moshe Ben Tov, the famous "Mezuza Rabbi". A very religious man walked in and when Rav Ben Tov saw him, he screamed out "Stop hitting your wife!".
The man was embarrassed and said "Yes, I have to come to you".
Rav Ben Tov replied "You don't have to come to me. You have to fix your deeds."
[Tzadik Hamezuzos, Page 52]
At the same hilula the Rav pointed to a young man and said "You aren't embarrassed for dating a goya?"
His girlfriend was sitting next to him and said "I am not a goya!" and left the hall in anger.
The boy's mother was also there and said "She is a kosher Jewess and they are getting married soon." The boy went up to Rav Ben Tov and they exchanged a few words after which Rav Ben Tov told them to call the girl back into the hall and said that they can get married with simcha and bracha.
It turned out that this girl was Jewish but the boy had another girlfriend on the side who was NOT Jewish......
[Page 53]
If Rav Ben Tov knew hidden things - Hashem certainly knows....