Everything has its indications and signs. Indications that knowledge is beneficial are that it leads to fine character, good manners and praiseworthy attributes. In this regard it was said:
“He whose knowledge doesn’t cause him to weep, can be justifiably considered not to have been granted beneficial knowledge,” since Allaah subhanahu wa ta’ala described the people of knowledge saying:
Say believe in it (The Qur’aan) or do not believe. Verily! Those who were given knowledge before it, when it is recited to them, fall down on their faces in humble prostration. And they say: “Glory be to our Lord! Truly, the Promise of our Lord must be fulfilled”. And they fall down on their faces weeping and it adds to their humility.”
Tawheed First 