Al-Imaam as-San’aanee (may Allah have mercy upon him) stated:

And the reality of (the prohibited, blameworthy) debating/argumentation is your speaking ill of the speech of other than yourself to display a deficiency in it for no other reason than belittling the one who said it and displaying your virtue over him.

Source: Subulus-Salaam 4/196

Translated by Abu Yusuf Khaleefah
12th of Dhul Qa’dah, 1436 H (08-27-2015)
Masjid Nur Allah, Queens, NYC

Original Arabic

✒ قال الإمام الصنعاني رحمه الله تعالى
( وحقيقة المراء : طعنك في كلام غيرك لإظهار خلل فيه لغير غرض سوى تحقير قائله وإظهار مزيتك عليه )
منقول

( سبل السلام 4/ 196)