Questor of Crassus in Syria in 53 B.C. After the unfortunate battle of Carrhæ, Syria, he became independent governor of the province, clearing it of the Parthians, and traversing all parts of the country in order to reestablish the fallen prestige of the Romans. Thus he came to Judea, where Pitholaus, a partizan of Aristobulus, had taken up arms against the Romans.
Cassius conquered the stronghold Tarichæa, killed the valiant Pitholaus at the instigation of Antipater, and carried away captive 30,000 Jews (Josephus, "Ant." xiv. 7, § 3; idem, "B. J." i. 8, § 9). He then went to Rome and was one of the conspirators against Julius Cæsar, who had appointed him pretor of Syria in 44. After Cæsar's murder he was sent as proconsul by the Senate in 43. Thus he came again to Judea, where, upheld by four Egyptian legions, he used his power to exact money from the Jews. The frightened Antipater quickly apportioned among the provinces the 700 talents of silver demanded by Cassius; and his son Herod was the first to pay his share. Malichus, however, the friend of Hyrcanus, seems to have hesitated, whereupon Cassius led away captive the inhabitants of the four cities Gophna, Emmaus, Lydda, and Thamma, and would have also killed Malichus, had not Hyrcanus appeased him with 100 talents ("Ant." xiv. 11, § 2; according to "B. J." i. 11, § 2, it was Antipater).
The Jews captured by Caius Cassius, as he is called, were liberated by a decree of Mark Antony ("Ant." xiv. 12, § 3), and it was ordered that Cassius' other depredations be repaired (ib. 12, § 5). During the war of Cassius and Brutus against Octavius Cæsar and Antony, Cassius, who was at that time in Syria, sought to gain the support of Herod by promising him the kingdom of Judea; Malichus was urged to poison Antipater ("Ant." xiv. 11, § 4; "B. J." i. 11, § 4). While Herod took the part of Cassius and the republicans, Malichus was looking forward to the victory of the Cæsarean party; so that it was in the interest of Cassius that Herod had the murderer of his father assassinated at Tyre, the old and weak Hyrcanus being induced to believe that the deed was instigated by Cassius ("Ant." xiv. 11, § 6; "B. J." i. 11, § 8). The anti-Herodian party joined issue with a certain Marion whom Cassius had left behind as master of Tyre; Herod, however, vanquished his enemies ("Ant." xiv. 11, § 7; 12, § 1; "B. J." i. 12, § 2) and thus put an end to Cassius' rule in Judea. Cassius soon after slew himself in the battle of Philippi, 42 B.C. ("B. J." i. 14, § 3).