‘I know your works - (behold I have set before you an opened door which none can shut) - that you have a little power, and have kept my word, and did not deny my name.'
The reference to the opened door clearly refers back in some way to the previous reference to the key and demonstrates that Jesus also controls the opportunities of witness and service (1 Corinthians 16:9; 2 Corinthians 2:12; Colossians 4:3) which He has opened up for them. It is clear that the works of the Philadelphians include faithful witness. They are not a powerful church, but they are faithful. They have held on to and obeyed the teaching of Jesus and, unlike Peter, they have been true to Him and have not denied His name. Nothing in fact is actually said against them, except perhaps their need to experience more of the power of the Spirit.
The opened door and the reference to He Who opens and none shuts parallels the time of Hezekiah when, as Israel perished, Judah witnessed a revival characterised by the reopening of the doors of the Temple when they had previously been ‘closed' (2 Chronicles 29:3). Compare also what is said about Eliakim, Hezekiah's treasurer, who was the opener of doors for the people demonstrating a new attitude towards the people (see above on Revelation 3:7). Thus the opened door includes the thought of revival. Hezekiah's time was the time of the open door. But eventually that door closed through the failure of the people. A warning to us all.