Garudapurana 1.218.5

1.218.5

evaṃ mātāmahādibhyaḥ /
etadācamanīyaṃ svāhā svadheti brāhmaṇahaste eṣavor'ghya iti brāhmaṇahaste puṣpadānam //

In the same manner, [offerings are made] to the maternal grandfathers and others. / Saying, "This water for sipping, svāhā, svadhā," into the hand of the brāhmaṇa, [and saying,] "This is your arghya offering," flowers are placed in the hand of the brāhmaṇa.