The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut  at sacred-texts.com
4. Because scripture directly states that.
'What a man does with knowledge, faith and the Upanishad is more powerful' (Kh. Up. I, 1, 10): this passage directly states that knowledge is subordinate to work 1, and from this it follows that mere knowledge cannot effect the purpose of man.
289:1 For the instrumental case 'vidyayâ' directly represents knowledge as a means of work.