Matthew 8:29

The demoniacs hated and feared Jesus. They recognized Him as Messiah, calling Him by the messianic title "Son of God" (cf. Matthew 3:17; Matthew 16:16; Luke 4:41). The disciples in the boat did not know who He was, but the demoniacs taught them. The demoniacs may have known Jesus from some previous contact (cf. Acts 19:15), or perhaps the demons were already speaking through them (cf. Matthew 8:31).

Their second question revealed their knowledge that Jesus would judge them one day. This was a messianic function. Evidently Jesus will cast them into the lake of fire when He sends Satan there (Revelation 20:10). [Note: Walvoord, Matthew: . . ., p. 67.] When Jesus cast out demons He was exercising this eschatological prerogative early. These demons asked if He planned to judge them then. He had cast out other demons recently (Matthew 4:24; Matthew 8:16). "Here" probably refers to the earth, where demons have a measure of freedom to operate, rather than to that particular locale.