From the earliest days of the Church, Christians understood the sacred Scriptures not as isolated literary artifacts but as living testimony entrusted to the community founded by Christ and guided by the Holy Spirit. The Word of God, written under divine inspiration, was received, proclaimed, interpreted, and preserved within the ecclesial body that Christ established. For this reason, the study of the textual history of the Old and New Testament cannot be separated from the life of the Fathers, the liturgy, the episcopal ministry, and the doctrinal consciousness of the early centuries. Textual criticism, in its patristic form, was never a merely academic pursuit. It was a pastoral and theological responsibility, exercised by bishops, theologians, and scholars who sought to safeguard the apostolic deposit and ensure that the Scriptures used in preaching, catechesis, and worship faithfully reflected the inspired originals. This book explores the textual criticism of the Old and New Testament as it developed in the patristic period, ending in the fifth century.