Bhagavad Gita Chapter 4.39
śraddhāvāḻ labhate jñānaḿ
tat-paraḥ saḿyatendriyaḥ
jñānaḿ labdhvā parāḿ śāntim
acireṇādhigacchati
Translation
A faithful man who is dedicated to transcendental knowledge and who subdues his senses is eligible to achieve such knowledge, and having achieved it he quickly attains the supreme spiritual peace.