C.H. Spurgeon emphasizes the assurance found in Isaiah 41:10, where God promises to strengthen us in times of service and suffering. He acknowledges our human weakness but reassures us that God's omnipotent strength is available to us, transforming our limitations into capabilities. Spurgeon reflects on personal experiences of receiving unexpected strength during trials, highlighting that divine support allows us to face challenges with courage and resilience. He encourages believers to rely on God's promise for strength, reminding us that our weaknesses can be overcome through His power.