Acts 9:24

but their laying await[plot] was known of Saul Perhaps from the information of some of the Christian disciples, who would be well disposed to Saul by what they had heard of him from Ananias, and who played the part of friends in aiding his escape from Damascus.

And they watched the gates day and night to kill him The gates were the places to which one fleeing from death would naturally make his way. St Paul says (2 Corinthians 11:32) of the circumstances under which this plot was made against his life, that "In Damascus the governor [Ethnarch] of King Aretas kept the city of the Damascenes with a garrison, desirous to apprehend me." Hence it appears that it was no mere attack made by the Jews resident in Damascus, but they had gained the support of the authorities for the time being. We do not know enough of the history of Syria and Arabia at this period to be able to explain with certainty how an Ethnarch of Aretas, who was king of Arabia Petræa, came to be holding Damascus. But we do know (Joseph. Antiq. xviii. 3. 1 4) that Aretas had been at war with Herod Antipas, Tetrarch of Galilee, who in consequence of his attachment to his brother Philip's wife, had forsaken his own wife, who was the daughter of Aretas. Herod had appealed to Rome, and been promised the help of the Roman power, but the death of Tiberius (a.d. 37) checked the march of Vitellius, the Roman governor of Syria, into Arabia, and he thereupon returned to Antioch. It may have been that Aretas, encouraged by this withdrawal, had advanced, and in the general confusion had taken possession of Damascus. He had, in a former stage of the war, destroyed the army of Herod; and some of the Jews, who hated Herod, spoke of this destruction of his troops as a Divine judgement for his murder of John the Baptist. We can understand then that the Jews in Damascus might under such circumstances favour Aretas, and in return for their support be aided by his Ethnarch in an attempt on the life of Saul.

Or the occupation of Damascus by Aretas may have been (as Dean Howson suggests) in consequence of the change of policy which took place so widely at the death of Tiberius; and Caligula, in contradiction of what his predecessor had been designing, to crush Aretas, may have put the Arabian king in command of the city of Damascus for a time.