Krishna now dismantles a common misunderstanding. Many people assume that if they simply stop doing things, they will reach a state of inner freedom. But stopping the hands does not stop the mind. True freedom from karma is a state of the mind, not of the body.
The second half drives the point further. Taking sannyasa (formal renunciation) by itself does not guarantee spiritual perfection either. Wearing ochre robes and sitting still is not the same as being genuinely free from attachment. The Gita's position is clear: it is not action that binds you. It is attachment within action.