Chapter 1. Despondency of Arjuna: Verse 42
पतन्ति पितरो ह्येषां लुप्तपिण्डोदकक्रिया: ||
Patanti pitaro hyeshaam lupta-pindodaka-kriyaah
The ancestors will be degraded when the rites of food & water offerings stop
Commentary & Explanation
When there is no maintenance of law in the society people will not adhere to laws & those practices which are assumed to be normal. Society will start doing undesirable things- adultery, killing each other, killing weak people, kidnapping, looting become new norm, leading to degradation of society.
It is an ancient belief that the souls of ancestors attain higher planes on the offerings of their descendants, those souls who are still in the material plane and not ascended to higher planes are said to live on offerings of their descendents.
Arjuna is using religious beliefs of his time to justify his stand.
|Kulasya||Of the family|
|Eshaam||Their; of them|
|Pinda||Offerings of food|