api svid bhagavān eṣa
yajño me khedayan manaḥ
dṛṣṭaḥ—just seen; aṅguṣṭha—thumb; śiraḥ—tip; mātraḥ—only; kṣaṇāt—immediately; gaṇḍa-śilā—large stone; samaḥ—like; api svit—whether; bhagavān—the Personality of Godhead; eṣaḥ—this; yajñaḥ—Viṣṇu; me—my; khedayan—perturbing; manaḥ—mind.
First of all this boar was seen no bigger than the tip of a thumb, and within a moment He was as large as a stone. My mind is perturbed. Is He the Supreme Personality of Godhead, Viṣṇu?
Since Brahmā is the supermost person in the universe and he had never before experienced such a form, he could guess that the wonderful appearance of the boar was an incarnation of Viṣṇu. The uncommon features symptomatic of the incarnation of Godhead can bewilder even the mind of Brahmā.
Link to this page: https://prabhupadabooks.com/sb/3/13/22