The sermon, based on Luke 18, explores the theme of humility through the parable of the Pharisee and the tax collector. The Pharisee prays with self-righteousness, boasting about his deeds, while the tax collector humbly pleads for God's mercy, acknowledging his sinfulness. The key takeaway is that true righteousness comes from a humble heart that recognizes its need for God's grace, rather than from self-justification or religious rituals. The pastor emphasizes that humility is a foundational aspect of Christian character and should be evident in our actions and attitudes towards others.