When there is no selfish involvement in work, the worker does not come to spiritual harm. The example is the lotus: it spends its life floating in water, yet the drops of water roll off its leaves without ever wetting them. Similarly, as long as the karma yogis do not expect reward or recognition, any evil that might stain them has nowhere to cling. Such yogis are said to be detached from the outcome or fruits of their actions (karma phala).
