Prajāpatigṛhītā

[Guest Francisco]

Hello, I am trying to translate a passage from the Kāṭhakasaṃhitā, 16, 19:

अयं पुरो भूस्तस्य प्राणो भौवायनो वसन्तः प्राणायनो गायत्री वासन्ती गायत्र्या गायत्रं गायत्रादुपांशुरुपांशोस्त्रिवृत्त्रिवृतो रथन्तरं वसिष्ट ऋषिः प्रजापतिगृहीतया त्वया प्राणं गृह्णामि प्रजाभ्यः

I think that the morphology and basic meaning of each word is clear, but I cannot figure out what is alluded to by the words प्रजापतिगृहीतया त्वया (instrumental singular feminine of प्रजापतिगृहीत, "seized by Prajāpati", and of the 2nd person singular pronoun, or instrumental singular feminine of the possessive pronoun corresponding to the 2nd person singular). I guess that those words agree with each other, but I cannot understand what all that refers to. If प्रजापतिगृहीतया takes the instrumental singular feminine form, it should be because it agrees with त्वया (instrumental singular too), and we should guess that त्वया refers to a female being, so the question is: who is that female being? Or, if त्वया is a form of a possessive pronoun, then प्रजापतिगृहीतया would be an adjective used as a noun, or with an elliptic noun. And then the question arises again: what is that noun? Can anybody help me?

Thank you very much in advance, and best regards for everybody.