Bhagavad Gita Verse 10, Chapter 5

brahmanyaadhaaya karmaani sangam tvyaktvaa karoti yaha |
lipyate na sa paapena padmapatramivaambhasaa || 10 ||
 
Having offered all actions to the eternal essence, and having cast off attachments, he who performs actions does not get tainted by sins, just like water does not taint a lotus leaf.
 
brahmani : eternal essence
aadhaaya : offered
karmaani : all actions
sangam : attachment
tvyaktvaa : cast off
karoti : perform action
yaha : one who
lipyate : taint
na : do not
saha : him
paapena : sins
padma-patram : lotus leaf
iva : like
ambhasaa : water
 
Previously, we came across the vision of one who has realized the self. He knows that he is not the doer of all his actions. But what about the one who has not realized the self, and who is still working to sublimate his selfish desires? What is his vision?
 
In this shloka, Shri Krishna says that the person who has not realized the self (that includes most of us) offers all actions in a spirit of devotion to Ishvara. Shri Krishna reiterates that if one has selfish desires, karma yoga is the ideal path to follow. The karma yogi works for a higher ideal such as Ishvara, but one who does not follow karma yoga works for the ego.
 
Shri Krishna brings Arjuna back to karma yoga with this shloka. Arjuna harbours desires, therefore Shri Krishna does not want him to jump straight into the yoga of renunciation, which is a totally different level.
 
Now, let's go a little deeper into the topic of attachment. Attachment can happen at four levels : attachment to the result of an action (I want a reward for singing this song), attachment to the action (I will sing a song only in my way), attachment to the sense of doership (I am singing this song) and attachment to the sense of non-doership (By not singing the song, I am the non-singer of this song). The first three are relatively easier to comprehend. The fourth one arises when one has not properly understood the notion of akarma or inaction from the fourth chapter.
 
So therefore, the karma yogi strives to transcend all four levels of attachment by offering results, actions, doership and non-doership to Ishvara. When he acts in the material world with such a vision, he does not accumulate any further desires, just like a lotus leaf does not get wet even though growing in water.