Bhashya
अत क्व तर्हि यजमानस्य लोक, यदर्थ यजते, न क्वचिल्लोकोऽस्तीत्यभिप्राय — ‘लोकाय वै यजते यो यजते’इति श्रुते ।लोकाभावे च स यो यजमान त लाकस्वीकरणोपाय सामहोममन्त्रोत्थानलक्षण न विद्यात् न विजानीयात्, सोऽङ्ग कथ कुर्यात् यज्ञम्, न कथचन तस्य कर्तृत्वमुपपद्यत इत्यर्थ ।सामादिविज्ञानस्तुतिपरत्वात् न अविदुषकर्तृत्व कममात्रविद् प्रतिषिध्यते— स्तुतये च सामादिविज्ञानस्य, अविद्वत्कर्तृत्वप्रतिषेधाय च इति हि भिद्येत वाक्यम् ।आद्ये च औषस्त्ये काण्डे अविदुषोऽपि कर्मास्तीति हेतुमवोचाम ।अथ एतद्वक्ष्यमाण सामाद्युपाय विद्वान्कुर्यात् ॥
In plain words
Where then is the world sought by the sacrificer for which he performs his rites? The objection is raised that no such world exists, based on the Vedic saying, 'He who sacrifices does so indeed for the sake of the world.' If worlds did not exist, and a sacrificer failed to understand the practice of acquiring the world through the rising chants of the Sama oblations, how could he possibly perform the sacrifice? Such a person would lack all qualification for ritual action. However, the text intends here to praise the contemplative knowledge of the Sama, not to prohibit ritual action to one who knows only outer rites—otherwise the sentence would have to split into two separate claims. As we explained in the Auṣastya section, ritual action belongs even to the unillumined. Therefore, the person who truly knows this meditative method involving the Sama should perform the sacrifice.
Close to the Sanskrit
Hence, where then is the world of the sacrificer, for the sake of which he sacrifices? The intention is that no such world exists, based on the scriptural text 'For the sake of the world indeed he sacrifices who sacrifices.' In the absence of a world, if that sacrificer does not know the method of appropriating the world—characterized by the rise of Sama oblations and mantras—how can he perform the sacrifice? By no means does agenthood belong to him, is the meaning. Because the purpose is to praise the knowledge of Sama and the like, not to prohibit the agenthood of one who knows only ritual action (for otherwise the sentence would split into two distinct purposes, praising knowledge and prohibiting ignorant agenthood). And we have already stated the reason in the earlier Auṣastya section that even an ignorant person has ritual action. Now, one who knows this method beginning with Sama should perform it.