Matthew Poole and continuators on Acts 19:8

8 And he went into the synagogue, and spake boldly for the space of three months, disputing and perswading the things concerning the kingdom of God.

Of the Iews at Ephesus. For in the greater Cities the Iews had their Synagogues in which they had their Prayers, read, and expounded the Law; as also a School for teaching of their Theology; in which they treated of hard Questions, and more difficult matters; which might occasion the Apostles frequenting that place.

The Gospel; which is so called, Rom. 14.17. because the Kingdom of Grace is by it set up in us here, and we are fitted by it for the Kingdom of Glory hereafter. But it might be also so called, because the Iews had dreamed of a political Kingdom of the Messiah, and the Christians would own that Christ was indeed a King, but that his Kingdom was a Spiritual Kingdom.