Bhashya
अथ जातकर्म ।जातेऽग्निमुपसमाधाय अङ्के आधायपुत्रम्, कंसे पृषदाज्यं संनीय संयोज्य दधिघृते, पृषदाज्यस्यउपघातं जुहोति 'अस्मिन्सहस्रम्' इत्याद्यावापस्थाने ॥
In plain words
Now comes the birth-rite. Once the child is born, the father lights the fire, sets the boy on his lap, mixes curds and ghee together in a bowl, and offers this pṛṣadājya into the fire, saying 'in this one, a thousand' and the rest of that formula, as he pours the offering.
Close to the Sanskrit
Now, the birth-rite (jātakarma). When [the child] is born, having kindled the fire, having placed the son on [his] lap, having brought together and blended curds and ghee into pṛṣadājya in a vessel, he offers the striking-oblation of the pṛṣadājya, [with] 'in this one, a thousand' and so on, at the occasion of pouring.