Bhagavad Gita 2.40नेहाभिक्रमनाशोऽस्ति प्रत्यवायो न विद्यते।स्वल्पमप्यस्य धर्मस्य त्रायते महतो भयात् ॥

If a religious ceremony is left uncompleted, it is a wastage as the performer cannot realise the fruits. But it is not so in the case of Karma Yoga because every action causes immediate purification of the heart.In agriculture there is uncertainty. The farmer may till the land, plough and sow the seed but he may not get a crop if there is no rain. This is not so in Karma Yoga. There is no uncertainty at all. Further, there is no chance of any harm coming out of it. In the case of medical treatment great harm will result from the doctors injudicious treatment if he uses a wrong medicine. But it is not so in the case of Karma Yoga. Anything done, however little it may be, in this path of Yoga, the Yoga of action, saves one from great fear of being caught in the wheel of birth and death. Lord Krishna here extols Karma Yoga in order to create interest in Arjuna in this Yoga.