I'm struggling with doubt in my spiritual practice. What does Chapter 50 say about the role of a Guru in overcoming doubt and ignorance?

Chapter 50 emphasizes that a Guru is indispensable for removing ignorance, which manifests from doubt (vikalpa). The text states that when doubt enters knowledge, even a wise person can become prideful, comparing it to how a single drop of fermented gruel can spoil an entire pot of milk. It is explicitly mentioned that ignorance "cannot be removed without a Guru." The process outlined in Chapter 50 is that by first understanding and removing ignorance with a Guru's help, the mind is purified. Only then can infinite knowledge manifest, leading to non-dual Samadhi.