Srimad-Bhagavatam: Canto 6 - Chapter 1 - Verse 54
Sanskrit:
सांवत्सरं पुंसवनं व्रतमेतदविप्लुतम् ।धारयिष्यसि चेत्तुभ्यं शक्रहा भविता सुत: ॥ ५४ ॥
ITRANS:
sāṁvatsaraṁ puṁsavanaṁvratam etad aviplutamdhārayiṣyasi cet tubhyaṁśakra-hā bhavitā sutaḥ
Translation:
Kaśyapa Muni continued: If you perform this ceremony called puṁsavana, adhering to the vow with faith for at least one year, you will give birth to a son destined to kill Indra. But if there is any discrepancy in the discharge of this vow, the son will be a friend to Indra.