Arabs helped Titus conquer Jerusalem in 70 AD

Interesting tidbit (thanks to Emet m'Tziyon). Publius Cornelius Tacitus mentions this in his Histories:
[5.1] EARLY in this year Titus Caesar, who had been selected by his father to complete the subjugation of Judaea, and who had gained distinction as a soldier while both were still subjects, began to rise in power and reputation, as armies and provinces emulated each other in their attachment to him. The young man himself, anxious to be thought superior to his station, was ever displaying his gracefulness and his energy in war. By his courtesy and affability he called forth a willing obedience, and he often mixed with the common soldiers, while working or marching, without impairing his dignity as general. He found in Judaea three legions, the 5th, the 10th, and the 15th, all old troops of Vespasian's. To these he added the 12th from Syria, and some men belonging to the 18th and 3rd, whom he had withdrawn from Alexandria. This force was accompanied by twenty cohorts of allied troops and eight squadrons of cavalry, by the two kings Agrippa and Sohemus, by the auxiliary forces of king Antiochus, by a strong contingent of Arabs, who hated the Jews with the usual hatred of neighbours, and, lastly, by many persons brought from the capital and from Italy by private hopes of securing the yet unengaged affections of the Prince. With this force Titus entered the enemy's territory, preserving strict order on his march, reconnoitring every spot, and always ready to give battle. At last he encamped near Jerusalem.

So while students of the Bible may not be surprised, Tacitus shows that Arab hatred of Jews pre-dates Islam by many centuries.

I imagine that they were only upset by the "occupation" of Canaanite land a millenium earlier, and that they were just trying to help the Romans uphold international law.

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By the way, Tacitus clearly hated Jews and Judaism, but some of his complaints (the few that are accurate) are actually quite complimentary to Western eyes:

This worship, however introduced, is upheld by its antiquity; all their other customs, which are at once perverse and disgusting, owe their strength to their very badness. The most degraded out of other races, scorning their national beliefs, brought to them their contributions and presents. This augmented the wealth of the Jews, as also did the fact, that among themselves they are inflexibly honest and ever ready to shew compassion, though they regard the rest of mankind with all the hatred of enemies. They sit apart at meals, they sleep apart, and though, as a nation, they are singularly prone to lust, they abstain from intercourse with foreign women; among themselves nothing is unlawful. Circumcision was adopted by them as a mark of difference from other men. Those who come over to their religion adopt the practice, and have this lesson first instilled into them, to despise all gods, to disown their country, and set at nought parents, children, and brethren. Still they provide for the increase of their numbers. It is a crime among them to kill any newly-born infant. They hold that the souls of all who perish in battle or by the hands of the executioner are immortal. Hence a passion for propagating their race and a contempt for death. They are wont to bury rather than to burn their dead, following in this the Egyptian custom; they bestow the same care on the dead, and they hold the same belief about the lower world. Quite different is their faith about things divine. The Egyptians worship many animals and images of monstrous form; the Jews have purely mental conceptions of Deity, as one in essence. They call those profane who make representations of God in human shape out of perishable materials. They believe that Being to be supreme and eternal, neither capable of representation, nor of decay. They therefore do not allow any images to stand in their cities, much less in their temples. This flattery is not paid to their kings, nor this honour to our Emperors.