Śatapatha Brāhmaṇa ("of a hundred paths") 1.7.3.18

1.7.3.18

uto anuṣṭubhāveva bhavataḥ | vāstvanuṣṭubvāstu sviṣṭakṛdvāstāvevaitadvāstu dadhāti pesukaṃ vai vāstu pisyati ha prajayā paśubhiryasyaivaṃ viduṣo 'nuṣṭubhau bhavataḥ

Or they are both anushtubh verses. The anushtubh is residue (or site, vâstu), and the svishtakrit also is residue: hence he thereby puts a residue to a residue. And, verily, one who knows this, and whose (invitatory and offering-formulas) are two anushtubh verses, his homestead (vâstu) is prosperous, and he himself prospers in regard to progeny and cattle.