Bethsur in tribu Iudae sive Beniamin. Et est hodie Bethsoro vicus euntibus nobis ab Aelia Chebron in vicesimo lapide, iuxta quem fons ad radices montis ebulliens ab eadem, in qua gignitur, sorbetur humo. Et apostolorum Acta referunt eunuchum Candacis reginae in hoc esse a Filippo baptizatum. Est et alla villa Bethsur in tribu Iudae mille passibus distans ab Eleutheropoli.
(Jerome 53:1-6)

Eusebius, Onomasticon 52:1-5 (ca. 295 A.D.); Jerome 53:1-6 (ca. 390 A.D.)
Beth-zur (Jos 15:58), in the tribe of Judah or Benjamin. And today there is a village called Bethsoro at the 20th milestone from Jerusalem on the way to Hebron, where is a spring, welling out from the foot of the mountain, and being absorbed by the same ground in which it comes forth; and the Acts of the Apostles report that the eunuch of Queen Candace was baptized here by Philip. There is also another Beth-zur, in the tribe of Judah, one mile from Eleutheropolis (Bayt Jibrin).

BIBLICAL BACKGROUND

Josh 15:21 .58 Places of the tribe of Judah
The towns belonging to the tribe of the people of Judah in the extreme South, toward the boundary of Edom, were... 58 Halhul, Beth-zur, and Gedor. 59 Maarath, Beth-anoth, and Eltekon: six towns with their villages.

1Mac 4:61 The fortress of Beth-zur
Judas stationed a garrison there to guard it; he also fortified Beth-zur to guard it, so that the people might have a stronghold that faced Idumea.

1Mac 6:28-31 The capture of Beth-zur
The king was enraged when he heard this. He assembled all his Friends, the commanders of his forces and those in authority. 29 Mercenary forces also came to him from other kingdoms and from islands of the seas. 30 The number of his forces was one hundred thousand foot soldiers, twenty thousand horsemen, and thirty-two elephants accustomed to war. 31 They came through Idumea and encamped against Beth-zur, and for many days they fought and built engines of war; but the Jews sallied out and burned these with fire, and fought courageously.

1Mac 11:63-66 Simon retakes Beth-zur
Then Jonathan heard that the officers of Demetrius had come to Kadesh in Galilee with a large army, intending to remove him from office. 64 He went to meet them, but left his brother Simon in the country. 65 Simon encamped before Beth-zur and fought against it for many days and hemmed it in. 66 Then they asked him to grant them terms of peace, and he did so. He removed them from there, took possession of the town, and set a garrison over it.

MORE ANCIENT SOURCES

Josephus, Antiquities 8, 246 (1st cent. A.D.)
Now Rehoboam, the son of Solomon, who, as we said before, was king of the two tribes, built strong and large cities, Bethlehem, and Etam, and Tekoa, and Bethzur, and Shoco, and Adullam, and Ipan, and Maresha, and Ziph, and Adoriam, and Lachish, and Azekah, and Zorah, and Aijalon, and Hebron.

Josephus, Antiquities12, 326 (1st cent. A.D.)
Judas also rebuilt the walls round about the city, and reared towers of great height against the incursions of enemies, and set guards therein. He also fortified the city Bethsura, that it might serve as a citadel against any distresses that might come from our enemies.

Itinerarium Burdigalense 599 (333 A.D.)
Fourteen miles away is Bethsur, at which is the spring where Philip baptized the eunuch. It is nine miles to Terebinthus An exceptionally beautiful basilica has been built there by command of Constantine.