The obligation to feed anyone who arrives is the strongest social rule in Punjab and it operates independently of religion, wealth or the relationship between the parties.
It has an institutional form in the langar and a domestic form in the household, and the two reinforce each other. A guest is fed before they are asked why they came.
The scale is sometimes absurd and is understood to be. Serving more than can be eaten is the point, and a guest who eats everything offered has failed to signal sufficiency.
This is the mechanism behind the Sikh disaster relief operations, the protest langars, the Gurdwara kitchens abroad, and the fact that a stranger can travel across Punjab and not go hungry.
It also drives wedding expenditure into debt, and both of those consequences come from the same rule.
If there is one thing about Punjab that survives every political and economic change described elsewhere on this site, it is that somebody will put food in front of you.
The obligation is to feed, and it is not conditional on who has arrived or why. Refusing food is difficult and offering it repeatedly is expected.
The langar is the institutional form of it and the household version predates and outlives any religious framing. A Punjabi Hindu, Muslim or Sikh house behaves the same way at the door.
It also has a cost. The pressure to serve more than a family can afford, at weddings and at funerals, is a real component of rural debt and is discussed as such in the villages themselves.