Charles Finney addresses the 'Hardness of Heart' in his sermon, emphasizing how the disciples, despite witnessing miracles, failed to understand due to their hardened hearts. He explains that hardness of heart is a voluntary state of mind, influenced by selfishness, which blinds individuals to truth and affects their feelings and judgments. Finney illustrates this with examples from scripture and personal observations, showing that a hard heart leads to misunderstanding, delusion, and a lack of genuine faith. He urges listeners to self-examine and recognize the state of their hearts, as true revival and understanding come from a softened heart open to God's truth.

David Wilkerson addresses the peril of a hardened heart, emphasizing that repeated rejection of God's warnings leads to an incurable state. He explains that hardness of heart is characterized by a refusal to obey God's Word and an immunity to the Holy Spirit's convictions. Wilkerson contrasts this with the transformative power of the gospel, illustrating how even the hardest of hearts can be softened when exposed to the truth. He warns that those who frequently hear reproof yet remain unresponsive are at the greatest risk of spiritual destruction. Ultimately, he highlights the importance of heeding God's messages to avoid the tragic fate of being beyond remedy.

David Wilkerson emphasizes the critical need for personal prayer, Bible reading, and the dangers of gossip and secret sin in his sermon 'This Is a Test.' He warns that neglecting these spiritual disciplines can lead to a hardened heart, making it difficult to withstand future trials. Wilkerson highlights the importance of heeding God's warnings and maintaining a close relationship with Him to prepare for challenging times. He urges listeners to reflect on their actions and attitudes towards prayer, gossip, and sin, as these can lead to spiritual decay. Ultimately, he calls for a return to genuine faith and obedience to avoid the pitfalls of a hardened heart.