Why is a Guru considered so important for removing ignorance, even for someone who is already wise?

As explained in Chapter 50, a Guru is essential because ignorance manifests from doubt (vikalpa), and this doubt cannot be removed without a Guru's guidance. The text emphasizes this point by noting that even a supreme knower like Shuka suffered a loss due to doubt. When doubt enters knowledge, it can cause even a wise person to become prideful. The text uses an analogy, stating that a single drop of fermented gruel can spoil a large pot of milk. Therefore, the Guru's primary role is to help a disciple first understand and then remove this ignorance, which purifies the mind. Only after this purification can infinite 'knowledge' manifest, leading to non-dual Samadhi.