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.
They are:
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