In plain words
To experience the fruit of these karmas done with desire for their fruit, he takes birth again. That is why: karmānu bandhini manuṣyalōkē. Man is bound by karma. Whatever karmas you do, when you do them in the spirit of offering them to Īśvara, they go on as sacred acts. The sādhaka must change all these natural karmas into karma-yoga. You must see the difference between karma and karma-yoga and act on it. What is done with desire for the fruit, with Ahaṅkāra and with selfishness is karma. All that is done without selfishness, without Ahaṅkāra and free of desire for the fruit is karma-yoga. Each one can decide for himself: 'Am I a karma-yogī, or one fallen from karma, or one who has charge of karma?' Man spends his time all the while as a creature of karma alone. But even when his karmas are bound up with selfishness, he must see to some extent the good of others and take part in service. To do karmas free of selfishness is man's chief mark. We must recognise the truth that this body came into being for the good of others, 'paropakārārthamidaṃ śarīram'. In service done like this for the good of others, a relationship given over to others comes into being. The rich, the middle class and the poor living together: that form alone is called society. Service to society means nothing but service to man. Today the rich man is able to rise to that position only through the help of his fellow man. Without the help of his fellow man, man can never reach a high station. So it is man's chief duty to say, 'It is through my fellow man that I have come to this position', to recognise his loyalty to him, and to give his fellow man fitting help.
In humanness there are three kinds of strength. The strength of wealth, the strength of the arm, the strength of learning. Man must set these three strengths on the path where he puts them to good use. Vitta is not only a word for wealth. Its meaning by derivation is vidyatē labhyatēiti. That is, it means 'that which is obtained'. The strength of the arm is something obtained. The strength of learning is something obtained. Wealth is something obtained. Vitta, then, may be called that which holds the three strengths together: the strength of wealth, the strength of the body and the strength of learning. To offer all three of these strengths one has obtained to society and put them to good use is man's chief mark.