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“And to the angel of the church in Philadelphia write; These things saith he that is holy, he that is true, he that hath the key of David, he that openeth, and no man shutteth; and shutteth, and no man openeth” (Revelation 3:7).
This verse applies Isaiah’s prophecy concerning Eliakim, to Christ (Isa. 22:20–22; 2 Kings 18:18). Eliakim was appointed to have supervision “over the household” of David, as signified by the fact that he was to be given “the key of the house of David.” Christ’s possession of the “key” represents His jurisdiction over the church (Matt. 28:18; Eph. 1:22).
Bible students understand that the close of the Philadelphia period (1844) marks the beginning of the investigative judgment described in Dan. 7:10; Rev. 14:6, 7. https://bibleask.org/what-is-the-significance-of-the-year-1844/
After the resurrection, Christ was granted full authority to open and to shut, to carry the plan of redemption to completion. Christ is our great high priest (Heb. 4:14, 15; 8:1), ministering in the sanctuary above, “the true tabernacle, which the Lord pitched, and not man” (Heb. 8:2, 6; Ex. 25:8, 9).
The ceremonies of the earthly sanctuary consisted of two parts, the daily service of ministration for sin, in the holy place, and the yearly service, on the Day of Atonement, which was considered a day of judgment, in the most holy place (Heb. 9:1, 6, 7; Dan. 8:11, 14).
And because the earthly sanctuary served as an “example and shadow of heavenly things” (Heb. 8:5) It can be concluded that the daily and yearly services of the earthly sanctuary have their counterpart in the ministry of Christ in the heavenly sanctuary.
So, the “shut door” would be that of the “holy place” of the heavenly sanctuary and the “open door” that of the “most holy place”, where Christ has been engaged in the work of the great antitypical day of atonement since that time. Thus, the “shut door” indicates the closing of the first phase of Christ’s heavenly ministry, and the “open door,” the beginning of the second phase.
In His service,