Mīmāmsa Sūtra 01.01.25
तद्भूतानां क्रियार्थेन समाम्नायः अर्थस्य तन्निमित्तत्वात् ॥१-१-२५॥
tadbhūtānāṃ kriyārthena samāmnāyaḥ arthasya tannimittatvāt ॥1-1-25॥
[तद्भूतानां (tadbhūtānām) - of those which have become that; क्रियार्थेन (kriyārthena) - by the purpose of action; समाम्नायः (samāmnāyaḥ) - recitation together; अर्थस्य (arthasya) - of the meaning; तन्निमित्तत्वात् (tannimittatvāt) - because of being its cause;]
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.)