Job 28:1

Description: Silver has the beginnings of its veins — allegorized by St. Gregory as Sacred Scripture being the vein from which true preaching draws

Preface and Praise of Sacred Scripture

Chapter II: On the Object and Breadth of Sacred Scripture — St. Gregory's explanation: "Silver is the brightness of speech or of wisdom; the veins are Sacred Scripture"
"Silver has the beginnings of its veins"