Chapter III Sloka 09

y}awaRTkmR[ae=NyÇ laekae=y< kmRbNxn>,
tdw¡ kmR kaENtey muKts¼> smacr .

loko'yaÕ karmabandhana× | 
tadarthaÕ karma kaunteya 
muktasaðga× sam˜cara ( 3|09)||

The world is bound by action
other than those performed 'for the sake of sacrifice';

Do thou, therefore, O Son of Kunti,
perform action for that sake (for yagna alone),
free from attachment.

Yagna here means:
"any self-sacrificing work undertaken in a spirit of Self-dedication for the blessing of all".  Such an action is not self-rewarding and, therefore, it is self-liberating.