Billy Sunday passionately preaches about the necessity of the 'Old Time Religion,' emphasizing that true salvation comes only through a personal relationship with Jesus Christ, not through church membership or theological understanding. He asserts that conversion is a complete transformation that requires a heartfelt confession of faith, and he denounces the apathy and sinfulness present in modern churches. Sunday encourages believers to seek a genuine revival that leads to a life of holiness and righteousness, and he stresses that salvation is a personal matter that cannot be achieved through others' efforts. He illustrates the power of faith and the importance of immediate action in accepting Christ, using biblical examples to demonstrate that true conversion can happen quietly and swiftly. Ultimately, he calls for a return to the foundational truths of Christianity, underscoring that it is only through Christ that one can be saved.