Tevet 6

"Know the G-d of your fathers and serve Him with a whole heart."1 Every sort of Torah knowledge and comprehension, even the most profound, must be expressed in avoda.2 I.e. the intellectual attainment must bring about an actual refinement and improvement of character traits, and must be translated into a deep-rooted inward attachment (to G-d) - all of which is what the Chassidic lexicon calls"avoda".