New Defender's Study Bible Notes
3:7 Philadelphia. Philadelphia means “brotherly love,” and was named by King Attalus of Pergamum, its founder, in honor of his brother. Philadelphia still survives as the modern town Alasehir, located about twenty-eight miles southeast of Sardis.
3:7 no man openeth. The Lord here claims to have “the key of David,” referring to Isaiah 22:22: “And the key of the house of David will I lay upon his shoulder; so he shall open, and none shall shut; and he shall shut, and none shall open.” In Isaiah’s context, this promise was made to Eliakim, a servant of King Hezekiah. The “key” was the key to the national treasury, and figuratively to control of the government. Eliakim thus was a type of the Messiah, and Christ here asserts in effect that He controls the governmental economy of the whole world and all that happens therein.