Srimad-Bhagavatam: Canto 9 - Chapter 1 - Verse 34

Sanskrit:

अमोघं देवसन्दर्शमादधे त्वयि चात्मजम् । योनिर्यथा न दुष्येत कर्ताहं ते सुमध्यमे ॥ ३४ ॥

ITRANS:

amoghaṁ deva-sandarśamādadhe tvayi cātmajamyonir yathā na duṣyetakartāhaṁ te sumadhyame

Translation:

The sun-god said: O beautiful Pṛthā, your meeting with the demigods cannot be fruitless. Therefore, let me place my seed in your womb so that you may bear a son. I shall arrange to keep your virginity intact, since you are still an unmarried girl.

Purport:

According to Vedic civilization, if a girl gives birth to a child before she is married, no one will marry her. Therefore although the sun-god, after appearing before Pṛthā, wanted to give her a child, Pṛthā hesitated because she was still unmarried. To keep her virginity undisturbed, the sun-god arranged to give her a child that came from her ear, and therefore the child was known as Karṇa. The custom is that a girl should be married akṣata-yoni, that is, with her virginity undisturbed. A girl should never bear a child before her marriage.