Skandapurana 6.3.70.3

6.3.70.3

ṣaṣṭhyāṃṣaṣṭhyāṃ nṛpaśreṣṭha hyaṣṭamyāṃ ca caturdaśīm .
snānaṃ yaḥ kārayenmartyaḥ śrāddhaṃ preteṣu bhaktitaḥ .
tasya pāpakṣayaḥ pārtha sūryaloke mahīyate .. 70.3 ..

On every sixth, O best of kings, as well as on the eighth and the fourteenth,
whatever mortal takes a bath and performs a śrāddha for the deceased spirits with devotion,
his sin is destroyed, O son of Pṛthā, and he is honored in the world of the sun.