Charles Finney emphasizes the profound need for a clean heart and a right spirit, as expressed in Psalm 51:10. He explains that this prayer signifies a deep desire for total sanctification, encompassing not just the will but the entire being, including thoughts and emotions. Finney outlines the conditions for offering this prayer acceptably, such as understanding one's sinfulness, sincere repentance, and a willingness to submit to God's transformative work. He warns against the dangers of ungoverned appetites and the necessity of recognizing one's dependence on God for moral cleansing. Ultimately, Finney encourages believers to seek a pure heart actively, trusting in God's willingness and ability to grant this request in their lives.