Q. What does it mean in Revelation 4.1 when it says “a door was opened” in Heaven?

A. This is a Hebrew idiom that literally means that a door of opportunity to discern spiritual truth and prophecy is being opened to a particular individual. In this case Yeshua has appeared to John on the island of Patmos. He has told him that many things are going to be revealed to him, including prophecies about the end times. Many of the things in the book of Revelation has been mentioned in other parts of the Scripture but John is going to get some insight on these things. So, in Revelation 4.1 a door (of opportunity to discern) was opened (for insight) in Heaven (where God is). This is alluding to several practices in the Temple that John would have known. The Tamid service is done twice a day ( Num 28). When the lamb was to be sacrificed 3 trumpets sounded and the massive doors to the Temple were opened and people gained access to the courts. Also, on several festivals the curtains of the Sanctuary were opened. This curtain had the stars of Heaven on them (7 planets that were visible) and this was seen as “the Heavens opening” and people could see into the Holy Place. This was to illustrate the concept that when you came to the Temple, kept the Torah that the God would reveal from the heavens (an open door) deeper insight to His plan, the Scriptures, prophecy or whatever. This is what is going on in Rev. 4.1. There are some who believe that this is also referring to the Natzal, or the “snatching away” of the believers before the Tribulation and that certainly is a possibility also. But, in the literal (peshat) level of interpretation this is referring to deeper insight was going to be given to John and to whoever reads and studies this book (Rev. 22.6).