Agniveshyagrihyasutra 2.5.10.19

2.5.10.19

sayati kṛṣṇo 'śvodbhirabhyukṣya udīrayathā marutaḥ samudrato yūyaṃ vṛṣṭiṃ varṣayathā purīṣiṇaḥ na vo dasrā upa dasyanti dhenavaḥ śubhaṃ yātāmanurathā avṛtsata iti \

If the black horse neighs when sprinkled with water, [he recites:] "Send up from the ocean, O Maruts! Rich in moisture, make the rain fall! Your milk cows, O wondrous ones, will not fail; chariots have turned in pursuit of those traveling in beauty."