Mīmāmsa Sūtra 01.01.25

The collective recitation (samāmnāyaḥ) of those entities which have attained that state, i.e. sentence formed by the collection of words, is for the purpose of action, because the meaning (artha) is caused by that.

(The sentence, which is a collection of words, conveys action as per the meaning caused by the individual word's meaning.)