A.B. Simpson emphasizes the importance of fully leaning on Jesus, akin to John resting on His breast at the Last Supper, as a demonstration of our love and trust in Him. He illustrates that true love for Christ involves casting all our cares upon Him without reservation, as He is capable of managing our burdens and fulfilling our needs. Simpson encourages believers to not only lean on Christ but also to feed on His life, highlighting that this resting and reliance is essential for the weary heart. He draws from the imagery of a heathen woman who sought confidence in her missionary, urging us to trust fully in the Lord. Ultimately, the sermon calls us to seek Jesus, asking where He nourishes His flock, as we lean upon Him.