Mīmāmsa Sūtra 01.01.05

śrautpattikastu śabdasya arthena sambandhaḥ। tasya jñānam upadeśaḥ avyatirekaḥ ca arthe anupalabdhe। tat pramāṇam bādarāyaṇasya anapekṣatvāt ॥5॥

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.