The central message of this sermon is that there are depths in relationships, particularly with God, that can be explored and experienced. The speaker emphasizes that having a relationship with Jesus Christ provides more than enough revelation and connection with God, but it also invites individuals to go deeper into the relationship by discovering new aspects of God's nature and character. This depth can be achieved through a greater understanding of Christ, who contains all the treasures of wisdom and knowledge. Furthermore, the speaker suggests that this deepening relationship is not about doing greater works or achieving more impressive miracles, but rather about experiencing the presence and power of God in one's life, particularly through the Holy Spirit. The takeaway for listeners is that they have the potential to experience a deeper level of connection with God, beyond mere familiarity or knowledge, by plumbing the depths of their relationship with Christ.