"These things"refer to the revelation of the messages to the seven churches (chs. 2-3; cf. 1:19). After John had received these messages, he received a vision of heaven in which Jesus Christ invited him (cf. 1:10, 12-16) to enter heaven to receive a revelation of future events. John had been viewing Christ in authority over the churches and their messengers (1:10-3:22), but now he would see a throneroom in heaven. "After these things I looked"is a clause that, with variations, introduces a new vision each time it occurs in Revelation (cf. 7:1, 9; 15:5; 18:1; 19:1). What John evidently saw in this vision was a door standing ajar (Gr. eneogmene) in the sky (cf. Ezek. 1:1). A voice, probably the glorified Christ's (cf. 1:10; Exod. 19:20, 24-25), bid him enter through the door into heaven. This is not an invitation for the church to enter heaven at the Rapture but an invitation for John to enter heaven in his vision. From that new vantage point he would receive new revelations (cf. Rom. 10:6; 2 Cor. 12:1-2). "Must"(dei) indicates that the events God was about to reveal will indeed happen. The word indicates divine necessity here as it does frequently in the Gospels, especially Luke's Gospel (Luke 2:49; 4:43; 13:33; 17:25; 19:5, 22; 22:37; 24:25-27, 44-46; cf. Acts 2:23-24).
