The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut [1896] at sacred-texts.com

33. (The soul is) an agent, on account of scripture having a purport (thereby).

In connexion with the doctrine that the soul possesses for its essence the qualities of the buddhi, another attribute of the soul is set forth.--The individual soul is an agent, because thus scripture has a purport. For only on that assumption scriptural injunctions (such as 'He is to sacrifice,' 'He is to make an oblation into the fire,' 'He is to give,' &c.) acquire a purport; otherwise they would be purportless. For they all teach special acts to be done by agents; which would not be possible if the soul did not possess the quality of being an agent.--On that supposition a meaning belongs to the following passage also, 'For it is he who sees, hears, perceives, conceives, acts, he the person whose Self is knowledge' (Pr. Up. IV, 9).