Mīmāmsa Sūtra 01.01.05

श्रौत्पत्तिकस्तु शब्दस्यार्थेन सम्बन्धः। तस्य ज्ञानमुपदेशोऽव्यतिरेकश्चार्थेऽनुपलब्धे। तत्प्रमाणं बादरायणस्यानपेक्षत्वात् ॥५॥

But, according to Bādarāyaṇa, the connection between a word or sound and its meaning is established by śruti; knowledge of this connection arises from authentic instruction and non-separation, even when the meaning is not (directly) perceived. This alone is the means of knowledge, since it does not depend on anything else.