Charles Ellicott Commentary Revelation 3:8

"I know thy works (behold, I have set before thee a door opened, which none can shut), that thou hast a little power, and didst keep my word, and didst not deny my name." — Revelation 3:8 (ASV)

I know your works: behold, I have set (better, given) before you an open door (better, a door opened). — A reference to the passages (Acts 14:27; 1 Corinthians 16:8–9; 2 Corinthians 2:12–13; Colossians 4:3) in which a similar expression is used reminds us that the open door was not simply a way of escape from difficulties, but an opening for preaching the gospel, an opportunity of doing good, as well as an abundant entrance into the kingdom.

For you have a little strength, and have kept my word, and have not denied my name. — The tenses used point back to some epoch in the history of this Church when some heavy trial or persecution arose, which tested the sincerity, fidelity, or Christian love of the faithful. “The reward then of a little strength is a door opened” (Dr. Vaughan).