KEY (מַפְתֵּחַ, H5158, an opener; κλείς, G3090, that which opens and closes.) An instrument, usually of wood, but sometimes of metal, for moving the bolt of a lock. Keys often were large. In OT times the key was worn on the shoulder as a symbol of authority (Isa 22:22; cf. Rev 3:7). In the NT the key fig. denotes power and authority, first and foremost, of Christ Himself (Rev 1:8). Certain angels are entrusted with the “key to the bottomless pit” (Rev 9:1; 20:1). The ability to teach is a key to the treasures of knowledge (Luke 11:52). The chief steward carried the keys of the household. The apostolate was entrusted with the “keys of the kingdom of heaven” (Matt 16:18, 19), a reference that is obviously fig. yet declarative of administrative responsibility in God’s kingdom. Thus the doors of the Church were opened by Peter at Pentecost (Acts 2) and at Caesarea (Acts 10), and by Paul and Barnabas in Asia Minor (Acts 14:27).