Vaishnava Dharmashastra 23.37

23.37

tasyopahatamātram apāsya gāyatryābhimantritaṃ suvarṇāmbhaḥ prakṣipet bastasya ca pradarśayed agneś ca ||

He must throw away thus much of it only as has been defiled, and must sprinkle over the remainder water, into which a piece of gold has been dropped, and over which the Gâyatrî has been pronounced, and must hold it tip before a goat (or before a horse) and before the fire.