|Chapter 1: Observing the Armies on the Battlefield of Kurukshetra|
kula-ghnanam kulasya ca
patanti pitaro hy esham
An increase of unwanted population certainly causes hellish life both for the family and for those who destroy the family tradition. The ancestors of such corrupt families fall down, because the performances for offering them food and water are entirely stopped.
So far Arjuna was making the point that the destruction of the varnasharama would destroy future generations. Now he makes the point that even the past generations in form of the departed ancestors would suffer since the offering of the oblations (pinda) to the ancestors would cease in an impious society. Pinda is not worship of ancestors but actually worship of Vishnu since it involves offering the remnants of Vishnu (prasadam) to the ancestors. By eating these remanants the sinful reactions of the ancestors are mitigated. The scriptures state that ancestors who are not offered oblations by their future sons have to suffer hellish conditions. Arjuna thus fears that this war will not only destroy future generations but also cause pain to the past generations and he would be held responsible for this. In the purport Srila Prabhupada gives the answer to this (which will become apparent later in the BG). The performance of devotional service relieves one of all ritualistic activities (SB 11.5.41).
Please read the Sanskrit Verse and the Prabhupada's Purport.