Sayyidi wa sanadi hazrat Mawlana Mohammad Taqi Usmani sahib db told us;
There are two extremely deadly sins very much prevalent in our days.
Even the seemingly religious individuals pay little attention to avoid these.
1. Sins committed by tongue. That is, engaging is lying, back-biting, vulgar or useless speech.
1. Inappropriate use of eyes. That is, seeing the prohibited (na mahram): lustful glances.
Special effort has to be made to abstain from them completely.”
Ramadan 1426 discourses