How does Chapter 4 characterize the nature and mission of saints who incarnate on earth?

Chapter 4 explains that saints are inherently liberated beings who choose to incarnate purely for the benefit of others, without any self-interest. Their primary mission is to uplift the distressed and protect the poor and weak. They work to restore the system of castes and stages of life and to destroy irreligion. The chapter uses a metaphor, stating that saints 'fill the foundation of Renunciation (Nivritti) and build the temple of Ultimate Truth' to awaken faith and guide devotees. Once their specific work is fulfilled, they conclude their incarnation, having completed their selfless task of re-establishing religion and guiding humanity back towards its ultimate well-being.