C.H. Spurgeon emphasizes the concept of sovereign mercy in his sermon 'I Will Cause the Shower to Come Down in His Season,' illustrating that only God has the authority to send rain, symbolizing grace. He explains that just as the earth needs rain for growth, humanity requires divine grace for spiritual sustenance, which is given abundantly and in its proper season. Spurgeon reassures that God's blessings are plentiful and varied, meant to meet our needs whether in times of drought or heaviness. He encourages believers to look to God for these 'showers of blessing' and to remain open to receiving His grace. Ultimately, the sermon highlights the necessity of God's grace in every aspect of life.