Albert Barnes on Acts 25:1

Now when Festus was come. Acts 24:27.

Into the province. The province of Judea; for Judea at that time was a Roman province.

After three days. Having remained three days at Caesarea.

He ascended. This was the usual language which described a journey to Jerusalem. Thus the English people speak of going up to London, because it is the capital. Acts 15:1.

To Jerusalem. The governors of Judea at this time usually resided at Caesarea; but as Jerusalem had been the former capital; as it was still the seat of the religious solemnities; as the sanhedrim held its meetings there; and as the great, and rich, and learned men, and the priests resided there, it is evident that a full knowledge of the state of the province could be obtained only there. Festus therefore, having entered on the duties of his office, early went to Jerusalem to make himself acquainted with the affairs of the nation.