Albert Barnes on Matthew 22:9

The highways. Literally, the exit or going out of the paths or roads. It means the square, or principal street, into which a number of smaller streets enter; a place, therefore, of confluence, where many persons would be seen, and persons of all descriptions. By this is represented the offering of the gospel to the Gentiles. They were commonly regarded among the Jews as living in highways and hedges--cast out, poor, and despised.