The Law Code of Yājñavalkya 1.10.205

1.10.205

iti smaraṇāt | śūdrāṇām apy etat kartavyam amantrakaṃ dvādaśe 'hni, evaṃ sapiṇḍīkaraṇaṃ mantravarjyaṃ śūdrāṇāṃ dvādaśe 'hni (ViDh 21.19–20) iti viṣṇusmaraṇāt | sapiṇdīkaraṇād ūrdhvaṃ sāṃvatsarikapārvaṇādīni putrasya niyamenaiva kāryāṇi, anyeṣām aniyatāni || 1.255 ||

This is to be performed by Shudras also, without mantras, on the twelfth day, since there is the smṛti text of Viṣṇu: "Thus the sapindaship rite is to be performed without mantras for Shudras on the twelfth day." Subsequent to the sapindaship rite, the annual pārvaṇa and other rites must necessarily be performed by a son; for others, they are not obligatory. || 1.255