Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 15: The Demigods Appeal to the Lord for Protection
Text 1.15.2

इष्टिं तेऽहं करिष्यामि पुत्रीयां पुत्रकारणात्।
अथर्वशिरसि प्रोक्तैर्मन्त्रैः सिद्धां विधानतः॥

iṣṭiṁ te ’haṁ kariṣyāmi putrīyāṁ putra-kāraṇāt
atharva-śirasi
proktair mantraiḥ siddhāṁ vidhānataḥ

iṣṭim te = an Iṣṭi sacrifice for your sake; aham = I; kariṣyāmi = shall perform; putrīyām = a sacrifice dedicated to generating sons; putra-kāraṇāt = so that you will have sons; atharva-śirasi = in the Atharva-śirā; proktaiḥ = declared; mantraiḥ = through mantras; siddhām = that sacrifice is accomplished; vidhānataḥ = in accordance with scriptural regulations.

In accordance with scriptural regulations, I shall perform an Iṣṭi sacrifice for your sake, a sacrifice dedicated to generating sons so that you will have sons. That sacrifice is accomplished through mantras declared in the Atharva-śirā.