This is the central teaching of the Bhagavad Gita. Its many shades are dealt with in several other verses, but here it is good to stress a factor often ignored.
‘Thy right is to work only’ implies that we have a right to work and to do, a right which we should exercise. This sentence is often read with the emphasis on ‘only’, but every word deserves emphasis and every emphasis will reveal a new interpretation! Karma will create the necessary circumstances around us and bestow on us the rewards of our own past actions. But, in those circumstances and with those rewards, we yet enjoy the freedom to work and to do what we care to. We are not asked to surrender this right, but to exercise it and thus not to ‘let thy attachment be to inaction’.
‘Not to the fruits thereof’ implies that there is someone else in charge of the reward – God. ‘Reward’ is euphemism for a ‘future event’. Leave it to him. This is not slave-mentality or fatalism. It is joyous participation in his plan. Joyous participation brushes aside ideas like: ‘Is God a capricious being who will visit us with pain though we do everything selflessly?’ The joy of doing what we can and should is itself the greatest and immediate reward. On the contrary, it is the man of hope who always suffers, even from the fear of the hope not being capable of realisation!