Garudapurana 2.25.41

2.25.41

vṛthā śrāddhaṃ vijānīyācchūdrānnena yathā dvijaḥ /
na prīṇayati tacchrāddhaṃ pitāmahamukhānpitṝn /
evaṃ jñātvā svagaśreṣṭha hīnajātīnsutāṃstyajet //

one should know that śrāddha to be in vain, like a twice-born [eating] food of a Śūdra; / that śrāddha does not gratify the ancestors headed by the grandfather. / Knowing this, O best of birds, one should abandon sons of low caste.