avatārī nārāyaṇa, kṛṣṇa avatāra
teṅha catur-bhuja, iṅha manuṣya-ākāra
avatārī—source of incarnations; nārāyaṇa—Lord Nārāyaṇa; kṛṣṇa—Lord Kṛṣṇa; avatāra—incarnation; teṅha—that; catuḥ-bhuja—four arms; iṅha—this; manuṣya—like a man; ākāra—form.
Because Nārāyaṇa has four hands whereas Kṛṣṇa looks just like a man, they say that Nārāyaṇa is the original God whereas Kṛṣṇa is but an incarnation.
Link to this page: https://prabhupadabooks.com/cc/adi/61