A.B. Simpson emphasizes Paul's testimony about his ministry in 2 Corinthians 4, highlighting the importance of humility, the transformative power of the Gospel, and the necessity of faithfulness in ministry. He illustrates how true credentials come from the lives changed through one's ministry rather than letters of recommendation, and he stresses that our sufficiency comes from God alone. Simpson also contrasts the old covenant with the new, showcasing the Gospel's ability to bring life and righteousness, and he calls for ministers to communicate with simplicity and earnestness, recognizing the eternal significance of their work. Ultimately, he warns against the distractions of worldly things that can blind people to the Gospel's light.