In the biblical world, documents were sealed with clay or wax (1 Kings 21:8; Job 38:14; Neh. 9:38; Jer. 32:10; Rev. 5:1). The integrity of the seal was assured by impressing an image into the soft substance, which would then harden and retain the unique image of the sender’s seal. The archaeological record attests this practice in the form of bullae (the impressions themselves, which survive long after the documents have disintegrated) as well as a large number of seals, which often were carved (Exod. 28:11; 39:6; Sir. 38:27; 45:11) into semiprecious stones or stone cylinders.
A person’s unique seal was closely identified with the owner and could be worn as a ring or pendant (see Gen. 38:18; Esther 8:8; Song 8:6). Besides documents, we have records of the sealing of caves (Matt. 27:66; cf. Dan. 6:17; 2 Macc. 2:5) and bags (Job 14:17; Tob. 9:5). In apocalyptic literature, seals are used to conceal prophecies of the future (Dan. 12:4) and to mark humans as belonging to God (Rev. 7:3–8).