Bhashya
न्पक्षे प्रागुक्तो यच्छब्दः उपास्यपरः; न प्रजापतिपरः ।स्त्रीपुंसोर्वा स्त्रीपुंसोश्च वा-शब्दः समुच्चयार्थः, 'वायुर्वा त्वा मनुर्वा त्वा' इत्यादौ दृष्टत्वात् ।एतदुक्तं भवति—उपास्येश्वरे सामन्यासं कृत्वा उपासकेन आत्मन्यपि सामन्यासः कार्यः ।य उपासकः इह लोके उत्कर्षेण स्थातुमपेक्षते, तस्मै सर्वैश्वर्यं ददाति ।देहान्ते तु देवः परं ब्रह्म तारकं व्याचष्टे, कामिनं प्रकृत्य देहान्ते इति विशेषणोपादानात् कामित्वेन प्रागधिकाराच्च ।निष्कामस्यार्वागपि देवः परं ब्रह्म तारकं प्रणवस्थं सामाङ्गं प्रणवेन व्याख्यातम्, येन प्रणवेन व्याख्यातेन अमृती भूत्वा स श्रोता अमृतत्वं च कैवल्यं प्राप्नोति ।यस्मात् तारकस्थं परब्रह्म व्याख्येयम्, तस्मादिदं तारकं साममध्यगं साममध्यवर्ति जपति, सामोपासनाङ्गप्रणवजपो यथाशक्तीति दर्शयति ।एतदेव आह—तस्मादिदं तारकं साम्नोऽङ्गं प्रजापतिः ऋषित्वेन ।यद्वा इदं तारकं परमेश्वरस्वरूपाख्यानेन, साम च परमेश्वरविषयविद्याप्रतिपादकमूलमन्त्राभिव्यञ्जकत्वेन, प्रजापतिरुभयकथनेन—इत्येतत्त्रितयमवश्यमुपासनायामङ्गम् ।एतदेव त्रितयमस्यामुपासनायामावश्यकमिति दर्शयितुं द्विरभ्यासः—तस्मादिदं सामाङ्गं प्रजापतिः तस्मादिदं सामाङ्गं प्रजापतिः इति ।
In plain words
...on this reading, the word 'yat' we looked at earlier points to the one being worshipped, not to Prajāpati. And 'whether woman or man' really means 'woman AND man' — 'vā' works here the way it works in phrases like 'Vāyu, or you; Manu, or you,' where it simply links rather than chooses between. Here is what all this comes down to: once you have placed the chant upon the Lord you worship, you, the worshipper, must place that same chant upon yourself too. Whoever wants to stand at the very top in this world, right now, is given exactly that — full sovereignty. But it's only at the moment of death that the god steps in and explains the highest Brahman, the syllable that carries you across — and that's because this promise was framed, from the start, for someone who still wants something, and his claim on it only opens up because he wants it. Someone with no desires left doesn't have to wait that long: for him, even now, the highest Brahman — that same crossing-syllable, resting inside the Om, itself a limb of this chant — is taught through the Om itself. And once that teaching lands, the one who hears it becomes immortal on the spot, gaining both immortality and the final aloneness beyond even that. Because the Brahman held inside this crossing-syllable has to be taught, the worshipper murmurs it — sitting right at the heart of the chant, right in its middle — showing that reciting the Om, as part of meditating on this chant, is done as far as one's strength allows. That's exactly the point being made: 'therefore this crossing-syllable is a limb of the chant' — and it counts as Prajāpati, because Prajāpati is its seer. Or, put differently: the crossing-syllable is a limb because it declares who the Lord truly is; the chant is a limb because it carries within it the very mantra that teaches all this; and Prajāpati is a limb because he is the one who states both. All three, together, are simply necessary — no meditation like this one works without them. And to make sure you don't miss how necessary they are, the line says it twice: 'therefore this is a limb of the chant — Prajāpati; therefore this is a limb of the chant — Prajāpati.'
Close to the Sanskrit
[...continuing from the previous page] — in this view, the previously mentioned word 'yat' refers to the object of meditation; it does not refer to Prajāpati. In 'strīpuṃsor vā,' it means 'of woman and man' — the particle 'vā' has the sense of combination, since it is seen used this way in passages such as 'vāyur vā tvā, manur vā tvā.' This means: having performed the placement of the Sāman upon the worshipped Lord, the worshipper must also perform the placement of the Sāman upon himself. Whichever worshipper wishes to remain, in this world, in a state of preeminence, to him he grants complete sovereignty. But at the end of the body, the deity explains the supreme Brahman, the Tāraka — this applies to a desirous one, because the qualifier 'at the end of the body' is taken with such a person in view, and because of his prior eligibility by virtue of being a desirer. But for the desireless one, even before death, the supreme Brahman, the Tāraka, situated in the Praṇava, the limb of the Sāman, is taught by the Praṇava itself; by which Praṇava, once taught, that hearer, having become immortal, attains both immortality and absolute isolation. Since the supreme Brahman situated in the Tāraka is to be taught, therefore he recites this Tāraka, which resides in, which stands in the middle of the Sāman; this shows that the recitation of the Praṇava, as a limb of the meditation on the Sāman, is according to one's ability. This very point he states: 'therefore this Tāraka is the limb of the Sāman' — and it is Prajāpati, by virtue of being its seer. Or else: this Tāraka is a limb by proclaiming the very nature of the supreme Lord; and the Sāman is a limb by manifesting the root mantra teaching the science concerning the supreme Lord; and Prajāpati is a limb by stating both — thus this triad is necessarily a limb in this meditation. In order to show that this very triad is necessary in this meditation, there is a double repetition: 'therefore this is the limb of the Sāman, namely Prajāpati; therefore this is the limb of the Sāman, namely Prajāpati' — thus.