One verse

Srimad Bhagavatam 3.20.43

3.20.43

त आत्मसर्गं तं कायं पितर: प्रतिपेदिरे । साध्येभ्यश्च पितृभ्यश्च कवयो यद्वितन्वते ॥ ४३ ॥

ta atma-sargam tam kayam pitarah pratipedire sadhyebhyas ca pitrbhyas ca kavayo yad vitanvate

te
they
atma-sargam
source of their existence
tam
that
kayam
body
pitarah
the Pitas
pratipedire
accepted
sadhyebhyah
to the Sadhyas
ca
and
pitrbhyah
to the Pitas
ca
also
kavayah
those well versed in rituals
yat
through which
vitanvate
offer oblations.

The Pitas themselves took possession of the invisible body, the source of their existence. It is through the medium of this invisible body that those well versed in the rituals offer oblations to the Sadhyas and Pitas (in the form of their departed ancestors) on the occasion of sraddha.