Bhagavad Gita Chapter 5.6
sannyāsas tu mahā-bāho
duḥkham āptum ayogataḥ
yoga-yukto munir brahma
na cireṇādhigacchati
Translation
Merely renouncing all activities yet not engaging in the devotional service of the Lord cannot make one happy. But a thoughtful person engaged in devotional service can achieve the Supreme without delay.