Bhagavad Gita 18.6 · Krishna
Do good, without clinging
एतान्यपि तु कर्माणि सङ्गं त्यक्त्वा फलानि च।
कर्तव्यानीति मे पार्थ निश्चितं मतमुत्तमम्॥
etānyapi tu karmāṇi saṅgaṃ tyaktvā phalāni cakartavyānīti me pārtha niścitaṃ matamuttamam
Yet even these should be done giving up clinging and the fruit. This, Partha, is My firm and highest view.
What it means
Krishna adds the key condition. Do these good acts, but without attachment, and without clinging to their rewards. Not for heaven, not for praise, not for good luck. This, he says, is his firm and highest conviction. It's the whole Gita in one line. Do good. Let go.
The story
Krishna rarely says this is my conviction so directly. Here he does. Arjuna hears the heart of his friend's teaching in one sentence.
In your life
Think of someone who donates blood regularly and never finds out who it helped. Do one good thing today and let it go completely.
Do good. Let go.