Sevā is service to God through service to others: cooking in the langar, cleaning the gurdwara, caring for the sick, washing the shoes of the congregation. Done without ego, it is itself worship. The idea is shared across Indian traditions, and in the Bhagavad Gītā it meets karma yoga, action offered without desire for its fruit.
Sevā
Selfless service, offered without thought of reward, as a form of devotion.
Also: Seva, sewa