SB 9.7.9

yadi vīro mahārāja
 tenaiva tvāṁ yaje iti
tatheti varuṇenāsya
 putro jātas tu rohitaḥ
Word for word: 
yadi — if; vīraḥ — there is a son; mahārāja — O Mahārāja Parīkṣit; tena eva — even by that son; tvām — unto you; yaje — I shall offer sacrifice; iti — thus; tathā — as you desire; iti — thus accepted; varuṇena — by Varuṇa; asya — of Mahārāja Hariścandra; putraḥ — a son; jātaḥ — was born; tu — indeed; rohitaḥ — by the name Rohita.
Translation: 
O King Parīkṣit, Hariścandra begged Varuṇa, “My lord, if a son is born to me, with that son I shall perform a sacrifice for your satisfaction.” When Hariścandra said this, Varuṇa replied, “Let it be so.” Because of Varuṇa’s benediction, Hariścandra begot a son named Rohita.