Manava Dharmashastra 1.12

1.12

sa bhagavān brahmā parivatsaraṃ saṃvatsaramuṣitvā tadaṇḍamakaroddvidhā | tāvatā kālena garbhaḥ paripacyate | tasminnaṇḍe sthita utpannaḥ sarvajñaḥ kathaṃ nirgaccheyamiti dhyātavān | aṇḍamapi tāvatkālena bhedajātaṃ paripākāt | ataḥ kākatālīyanyāyena tadaṇḍamakaroddvidhetyucyate |

That supreme lord, having dwelt in that egg for a y ear, himself, by his own thought, broke that egg into two parts.—(12)

Medhātithi’s commentary (manubhāṣya):
‘That Supreme Lord,’ Brahmā,—‘for a year,’ during a year,—‘having dwelt in that egg,’—the omniscient one, who had come into existence and was seated in the egg, thought of the way in which he would come out of it;—‘he broke the egg into two parts’;—one year is the time which the embryo takes for its development; so that after a year the egg, having reached its full development, burst (really), by reason of its full development having been reached. It is thus a chance coincidence that the egg burst just at the time that Brahmā was thinking of coming out; and it is in view of this coincidence that he is described as having broken the egg into two parts.—(12)

Parivatsaram—Kullū. alone takes this to mean ‘a year of Brahmā’; all others take it in the sense of the ordinary year; Cf. Śatapatha Brāhmaṇa 11. 1. 6. 2.

Dhyānāt—Medhātithi’s robust intellect again asserts itself: The Egg broke, not because the indwelling Brahmā willed it, hut because of its full development; and this coincided with Brahma’s wish to come out.