Shatapatha Brahmana 11.4.1.15

11.4.1.15

atha yadājyahaviṣaḥ prayājā bhavanti tasmātkumārasya retaḥ siktaṃ na sambhavatyudakamivaiva bhavatyudakamiva hyājyamatha yanmadhye yajñasya dadhnā puroḍāśeneti yajanti tasmādasya madhyame vayasi sambhavati drapsīvaiva bhavati drapsīva hi reto'tha yadājyahaviṣa evānuyājā bhavanti tasmādasya punaruttame vayasi na sambhavatyudakamivaiva bhavatyudakamiva hyājyam

And inasmuch as the fore-offerings have ghee for their offering-material, a boy's seed is not productive, but is like water, for ghee is like water; and inasmuch as, in the middle of the sacrifice, they sacrifice with sour curds and with cake, therefore it is productive in his middle stage of life, for thick-flowing, as it were, is (that havis), and thick-flowing, as it were, is seed; and inasmuch as the after-offerings have ghee for their offering-material, it again is not productive in his last stage of life, and is like water, for ghee, indeed, is like water.