Bhagwad Gita
Chapter 4, Verse 18
कर्मण्यकर्म यः पश्येदकर्मणि च कर्म यः।
स बुद्धिमान् मनुष्येषु स युक्तः कृत्स्नकर्मकृत्।।4.18।।
One who sees inaction in action, and action in inaction, is intelligent among men, and he is in the transcendental position, although engaged in all sorts of activities.