Bhashya
अथामूर्तम्- अथाधुना अमूर्तमुच्यते ।वायुश्चान्तरिक्षं च यत्परिशेषितं भूतद्वयम्- एतत् अमृतम्, अमूर्तत्वात्, अस्थितम्, अतोऽविरुद्धमानं केनचित्, अमृतम्, अमरणधर्मि; एतत् यत् स्थितविपरीतम्, व्यापि, अपरिच्छिन्नम्; यस्मात् यत् एतत् अन्येभ्योऽप्रविभज्यमानविशेषम्, अतः त्यत् 'त्यत्' इति परोक्षाभिधानार्हमेव- पूर्ववत् ।तस्यैतस्यामूर्तस्य एतस्यामृतस्य एतस्य यतः एतस्य त्यस्य चतुष्टयविशेषणस्यामूर्तस्य एष रसः; कोऽसौ? य एष एतस्मिन्मण्डले पुरुषः- करणात्मको हिरण्यगर्भः प्राण इत्यभिधीयते यः, सएषः अमूर्तस्य भूतद्वयस्य रसः पूर्ववत् सारिष्ठः ।एतत्पुरुषसारं चामूर्तं भूतद्वयम्-हैरण्यगर्भलिङ्गारम्भाय हि भूतद्वयाभिव्यक्तिरव्याकृतात्; तस्मात् तादर्थ्यात् तत्सारं भूतद्वयम् ।तस्य ह्येष रसः- यस्मात् यः मण्डलस्थः पुरुषो मण्डलवन्न गृह्यते सारश्च भूतद्वयस्य, तस्मादस्ति मण्डलस्थस्य पुरुषस्य भूतद्वयस्य च साधर्म्यम् ।तस्मात् युक्तं प्रसिद्धवद्धेतूपादानम्- तस्य ह्येष रस इति ॥
In plain words
'Now the formless' means: right here, it's the formless side's turn. Wind and space are what's left once everything else is accounted for, and this pair is immortal precisely because it's formless and unfixed — nothing can stop it, so it never dies. This is 'yat': the opposite of fixed, spread everywhere, without limit. And because it has a quality that can't be clearly told apart from anything else, it's called 'tyat' — a word that, as before, can only ever point at something from a distance. Add up the formless, the immortal, the 'yat', and the 'tyat', and their essence comes down to one thing: who is it? The person living in that orb, the one called Hiraṇyagarbha, the breath that works like an instrument — he is the finest essence of the formless pair of elements, just as the sun was for the formed ones. And that pair takes him as its essence for a simple reason: their whole coming-forth out of the Unmanifest exists so that Hiraṇyagarbha's subtle body can arise. That's the entire point of it, which is why they carry him as their essence. And here's why the comparison holds: the person in that orb, unlike the orb itself, can't be seen directly — and neither can the essence of the elements. Both stay hidden in exactly the same way, so the person in the orb and the pair of elements really are alike. Which is why the same reasoning used before can simply be reused here: 'for this is its essence.'
Close to the Sanskrit
'Now the formless' — now, at this point, the formless is being explained. Wind and space, the pair of elements that remain — this is immortal, because it is formless, and unfixed; therefore, meeting no obstruction from anything, it is immortal, never subject to death. 'This is yat' — the opposite of the fixed, all-pervading, unlimited. Since this, whatever it is, has a particularity not clearly differentiated from other things, therefore it is 'tyat' — the word 'tyat' is fit only for indirect designation, just as before. Of that, of this formless, of this immortal, of this yat, of this tyat — worth of the four attributes of the formless — this is the essence. Who is that? The one who is this person in this orb — who is called Hiraṇyagarbha, the breath having the nature of an instrument — he is this: the essence, the finest essence as before, of the pair of formless elements. And this pair of formless elements takes this person as its essence — for the manifestation of the pair of elements out of the Unmanifest exists in order to bring about the subtle body of Hiraṇyagarbha; therefore, since that is the whole point of it, the pair of elements has him as its essence. For this is its essence — because the person situated in the orb, unlike the orb itself, is not directly perceived, and neither is the essence of the pair of elements; therefore there is a likeness between the person situated in the orb and the pair of elements. Therefore it is fair to reuse the already-established reasoning: 'for this is its essence.'