Can you explain what Chapter 45 means when it says 'the Guru alone is the true Brahman' and what is 'undifferentiated worship'?

Chapter 45 presents a profound spiritual concept by stating that 'Brahman is eternal, the world is transient; the Guru alone is the true Brahman.' This identifies the Sadguru not just as a guide but as the embodiment of the ultimate, eternal reality. The path forward, as described in the chapter, is to renounce the transient world and meditate solely on the Guru. This constancy of feeling leads to dispassion (Vairagya). The text then defines the Sadguru as a 'solid mass of Brahman-consciousness.' When this realization is achieved, divinity arises in all beings, leading to what is called 'undifferentiated worship' (Abheda-bhajan), where the devotee sees the divine in everything without distinction.