Jean-Pierre de Caussade's book, On Prayer (also known as A Treatise on Prayer from the Heart or Spiritual Dialogues on Different Kinds of Prayer), is a comprehensive spiritual guide that leads readers into profound mystical prayer. Its core teaching is total surrender to the divine will manifested in every moment of daily life, which he calls the 'Sacrament of the Present Moment'. Caussade emphasizes that true prayer must come from the center of one's being or heart, as opposed to mere verbal or intellectual prayer. It includes inner silence and attentive pauses. The book's central message is that God is present and at work in every event, task, and suffering of daily life, not just in extraordinary spiritual experiences. The path to true holiness and peace lies in completely abandoning one's own will and accepting everything that happens as a manifestation of God's providential will and love. In short, On Prayer teaches that by recognizing and embracing God's will in every aspect of daily life, one can achieve a profound and transformative relationship with God.