Revelation 3:8

an open door Through which thou mayest enter into the Kingdom, into the house of David.

and no man can shut it Probably the false Jews mentioned in the next verse denied the title of the Christians in Philadelphia to the privileges of brotherhood whence we may suppose that they were mostly Gentiles. Christ answers, that He would grant what they refused.

for thou hast Rather, that thou hast, depending on "I know thy works," the intermediate words being parenthetical.

thou hast a little strength Better, thou hast little strength and [yet] hast kept &c. The point is that his strength is not great, not that he has a little left in spite of the strain upon it.