Skandapurana 5.223.12

5.223.12

ṣaṣṭhyā vibhaktyā tu teṣāmāsanaṃ ca pradāpayet ..
ṛjubhiḥ sākṣatairdarbhaiḥ sodakairdakṣiṇāṃgataḥ .. 12 ..

He should offer them a seat with the genitive case ending, / using straight darbha grass with unbroken rice grains and water, from the right side;