सर्वकर्माणि मनसा संन्यस्यास्ते सुखं वशी। नवद्वारे पुरे देही नैव कुर्वन्न कारयन् ॥

sarva-karmāṇi manasā sannyasyāste sukhaṁ vaśhī nava-dvāre pure dehī naiva kurvan na kārayan

Mentally renouncing all actions, the sovereign dweller in the body resteth serenely in the nine-gated city, neither acting nor causing to act.

In plain words: Krishna says that the person living in the body lets go of all actions in their mind and rests calmly. The body is like a city with nine gates, meaning its openings like the eyes, ears and mouth. The true self in it neither acts nor makes anything act.