According to Shankara, the entire Veda is important in that, till the seeker reaches the stage of pursuing the higher knowledge (jñana kanda) the duties enjoined in the other parts (karma kanda) are necessary for him. Otherwise, the Veda would not teach them. So, a spiritual seeker has to undertake scriptural study.
The path of action (karma yoga), states Shankara, is the ‘means to the supreme bliss indirectly’ in that it prepares the mind of the spiritual aspirant for knowledge, and thereby makes him competent for adopting the path of knowledge (jnana yoga), which is the direct path to liberation. Man cannot abstain from action, and as action binds man by resulting in karma… it is essential to know how to act without accruing further karma. This is the secret of action, called naiskarmya in the Gita… true renunciation is a mental disposition wherein the mind becomes serene without the distractions of the world.
(Spiritual Path). The Roots of Vedanta – Selections from Shankara’s Writings, p. 326