This book is an instrument valuable for all students of the Theological courses, who at the end of their academic preparation, intend to be ordained priests, and for all Christians who want to come to know their own priestly dignity. It is not an exhaustive study of the Letter to Hebrews, nor a complete and adequate reflection on their priesthood. Rather it is a study guide with the aim of helping all the candidates for priesthood. Rather it is a study guide with the aim of helping all the candidates for priesthood to deepen their understanding of the role and position of the ordained priest, since we have amply realised how ministerial priests are separated from their flocks and, very often they rule over them in an inappropriate manner. This book will lea the students of theology and other readers into the cultic system of the Old Testament in all its components, in order to see how it is articulated in view of a comparison with Christ's priesthood. This will help the readers to consider the person of Jesus, in order to understand whether his activity and teaching, in one way or another, were related to the idea of priestly office of old. The study makes it evident that Jesus' deeds and words, together with his death on the cross, have nothing to do with the sacrificial system of the Old Testament.