The text says 'Only from knowledge comes liberation,' but also that knowledge is impossible without destroying sinful karma. How can one navigate this apparent contradiction to achieve liberation?

This is not a contradiction but a sequence of spiritual progression. Chapter 50 affirms the Vedic theorem, "Only from knowledge comes liberation." However, it immediately clarifies that "without the destruction of sinful karma, the dawn of knowledge is impossible." This means that purifying oneself from past actions is a prerequisite. Furthermore, the text explains that ignorance, which manifests from doubt, must be removed to purify the mind. This process of removing doubt cannot be accomplished without a Guru. Therefore, as Chapter 50 outlines, the path involves addressing sinful karma and then, with a Guru's help, removing the doubt that fosters ignorance. Only when the mind is thus purified can infinite 'knowledge' manifest, leading to liberation.