Adam Clarke on Revelation 3:8

I have set before thee an open door - I have opened to thee a door to proclaim and diffuse my word; and, notwithstanding there are many adversaries to the spread of my Gospel, yet none of them shall be able to prevent it.

Thou hast a little strength - Very little political authority or influence; yet thou hast kept my word - hast kept the true doctrine; and hast not denied my name, by taking shelter in heathenism when Christianity was persecuted. The little strength may refer either to the smallness of the numbers, or to the littleness of their grace.