शतधा रमुत्समक्षी जमानम विपस्थितम वितारम वक्वानाम | हेलिम्दनतम वित्रो रुपस्थेतम्रो जतिपिप्रतम सत्यवाचम ||
sorry for the spelling mistakes.
It took some effort, but I've found the verse you're referring to. It's verse 9 of Rig Veda Book 3 Hymn 26:
śatadhāramutsamakṣīyamāṇaṃ vipaścitaṃ pitaraṃ vaktvānām |
meḷiṃ madantaṃ pitrorupasthe taṃ rodasī pipṛtaṃ satyavācam ||
The Spring that fails not with a hundred streamlets, Father inspired of prayers that men should utter,
The Sparkler, joyous in his Parents' bosorn, him, the Truth-speaker, sate ye, Earth and Heaven.
The translation isn't very clear, so for more explanation we can turn to the Anukramani information given in my answer here. As you can see, Rig Veda Book 3 Hymn 26 was heard by the gods by the sage Vishwamitra, and is addressed to Agni the fire god. But there's additional complication when it comes to verse 9.
Here is what sage Shaunaka says about verse 9 in this excerpt from the Brihaddevata:
The last (stanza), 'With a hundred streams' (śatadhāram: iii.26.9), is in praise of a preceptor.
Which preceptor is it in praise of? For that we can turn to Sayana's commentary on the Rig Veda, which says this:
Heaven and earth be kind to that sage who is as it were a many- channelled and inexhaustible stream(of knowledge); the parent (of his disciples), the collater of holy texts, rejoicing on the lap of his parents,, whosewords are truth. [That sage: That is, Vis'va_mitra himself; in consequence of his discovery that vais'va_nara is para-brahma the supreme spirit]
In other words, whereas the rest of the hymn was heard from the gods by the sage Vishwamitra and is in praise of Agni the fire god, this verse was heard from the gods by Agni the fire god and is in praise of Vishwamitra! Vishwamitra is being praised for discovering that the being that lies at the heart of Agni the fire god is Brahman. It's similar to what the Upanishads say about the sage Vamadeva, whom I discuss in this question.
But I imagine that these subtleties are ignored in the Yagna you heard, and the entire hymn is just recited as a hymn to Agni.