प्रवृत्तिं च निवृत्तिं च कार्याकार्ये भयाभये। बन्धं मोक्षं च या वेत्ति बुद्धिः सा पार्थ सात्त्विकी ॥

pravṛittiṁ cha nivṛittiṁ cha kāryākārye bhayābhaye bandhaṁ mokṣhaṁ cha yā vetti buddhiḥ sā pārtha sāttvikī

That which knoweth energy and abstinence, what ought to be done and what ought not to be done, fear and fearlessness, bondage and liberation, that Reason is pure, O Pârtha.

In plain words: Pure understanding knows when to act and when to hold back. It knows right from wrong duty, what to fear and what not to fear, and what traps us and what sets us free. Krishna calls Arjuna Partha, son of Pritha.