ISB ~ Revelation 3 v7

Philadelphia:Twenty-eight miles southeast of Sardis. Philadelphia served as a base for spreading Greek culture throughout the highlands of central Asia Minor. It was also home to a synagogue community hostile to Christians.

key of David:A symbol of royal Davidic authority. Jesus holds this key as a descendant of David (Rom 1:3) and the messianic heir to his throne (Lk 1:32).

• The expression comes from Is 22:22, where the keys of the house of David pass from one prime minister to another. Being the Davidic king, Christ possesses the fullness of royal power, yet the Church is given a share in his authority. See note on Mt 16:19.