Not a single living entity can remain unengaged even for a moment. One must act by his natural tendency according to the three modes of material nature because this natural tendency forcibly makes him work in a particular way.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
न हि कश्चित्क्षणमपि जातु तिष्ठत्यकर्मकृत् । कार्यते ह्यवशः कर्म गुणैः स्वाभाविकैर्बलात्
na hi kaścitkṣaṇamapi jātu tiṣṭhatyakarmakṛt | kāryate hyavaśaḥ karma guṇaiḥ svābhāvikairbalāt
SB 6.1.53