Devils (daimonia). Demons it should be translated always. Suffered not (ouk hpien). Would not allow, imperfect tense of continued refusal. The reason given is "because they knew him" (oti hdeisan auton). Whether "to be Christ" (Criston einai) is genuine or not, that is the meaning and is a direct reference to Matthew 1:24 when in the synagogue the demon recognized and addressed Jesus as the Holy One of God. Testimony from such a source was not calculated to help the cause of Christ with the people. He had told the other demon to be silent. See on "Mt 8:29" for discussion of the word demon.