The name of Poseidonius is not a name well-known to people outside of classicist circles, but he was, in fact, one of the most important authors of his time. As, like Aristotle, Poseidonius was a polymath who lived between 186 BC to 86 BC writing on numerous different subjects and whose works informed many later historians in antiquity such as Strabo (who mentions using him more than once). We can further illustrate the importance of Poseidonius by pointing out that his stridently anti-jewish student Apollonius Molon was actually the tutor of two of the greatest and best known Roman statesmen: Julius Caesar and Cicero.
Poseidonius has been largely left out of the anti-jewish canon of Graeco-Roman authors who wrote against the jews in part because none of his works have survived the ravages of history and we know him only through the numerous mentions he receives in work of others that has survived. What we know of his anti-jewish views however comes primarily from Josephus' philippic against the anti-jewish Greek scholar Apion of Alexandria and whose views Josephus attempts to trace back to Poseidonius through Apollonius Molon (both of whom Apion cited according to Josephus).
For the sake of clarity I reproduce the whole of Josephus' mention of Poseidonius' views on the jews:
'I am no less amazed at the proceedings of the authors who supplied him with his materials, I mean Poseidonius and Apollonius Molon. On the one hand, they charge us with not worshipping the same gods as other people; on the other hand, they tell lies and invent absurd calumnies about our temple, without showing any consciousness of impiety. Yet to high-minded people nothing is more disgraceful than a lie, of any description, but above all on the subject of a temple of world-wide fame and commanding sanctity. Within this sanctuary Apion has the effrontery to assert that the Jews kept an ass's head, worshipping that animal and deeming it worthy of the deepest reverence; the fact was disclosed, he maintains, on the occasion of the spoliation of the temple by Antiochus Epiphanes, when the head, made of gold and worth a high price, was discovered . . .' (1)
If what Josephus has to say here is correct then it is truly libellous attack the jews, but then as we have already pointed out in relation to the claims that he makes about Pythagoras of Samos (2) and Clearchus of Soli: (3) Josephus is not a dispassionate historical source. Indeed in these two instances we have shown Josephus' willingness to lie about/knowingly misrepresent his sources to support his attack on Apion's work. This is hardly surprising considering how overtly politicised 'Against Apion' is and how Josephus is trying to challenge the Graeco-Roman intellectual consensus on Judaism (especially in relation to its origins and antiquity [the two factors which governed respect and consensus of opinion on the authority of a religion in the ancient world]).
It is thus rather ironic that Josephus asserts that to 'high-minded people nothing is more disgraceful than a lie' and spends the better part of a paragraph stating that the Poseidonius and Apollonius Molon 'invent absurd calumnies' against the jews.
Historians have - on the basis of Josephus' assertion - frequently brushed aside the arguments of Posidonius against the jews, but in doing so they have tended to forget that while Josephus may make often and forthright claims to being the fountain of all truth: this is very far from being the case.
Josephus tells us that the Poseidonius relates that the Selucid monarch Antiochus (IV) Epiphanes when entering the Temple of Solomon discovered a statue of a golden ass that the jews reverenced and worshipped. This story actually dates from one or either of the earlier Greek authors Mnaseas of Patra (writing slightly before Poseidonius) and Damocritus (probably writing at about the same time if not slightly before Poseidonius) likely reflecting a source of some description that had come to light rather than the claim - based on Josephus' own words - that these writers had invented the charges as a quite literal 'blood libel' of whole cloth.
The story of a golden ass should immediately cause us to prick up ears up to the potential of the story being based on fact: why?
Well remember that the Book of Exodus relates that the jews worshipped a 'Golden Calf' (the Egyptian goddess Hathor) indicating a proclivity for worshipping other gods. It just so happens that one of the Canaanite goddesses - Canaanite religion being where Yahweh comes from incidentally - had a horse (easily transliterated into 'ass' to make it less complimentary vis-à-vis Greek polemical wordplay) as one of her representative aspects. (4) That Canaanite goddess was the fertility goddess Astarte: who was taken from Canaanite paganism and incorporated into Judaism as what we now call the Shekhina (sometimes called 'God's Wife'). (5) We also know from Kings 1 and 2 of the fact that Astarte worship was a recurring theme in the time of Solomon and even received a form of official sanction and that the worshippers of Yahweh were desperate to crush the cult. (6)
Bearing all this in mind then we can retrace the events of Antiochus (IV) Epiphanes entry into the temple of Solomon and his finding a statue of a golden horse - the representation of Astarte - in the Holy of Holies that had been kept among the temple ornaments since at least the time of Solomon. We must bear in mind that the Holy of Holies in the temple was a place that only the high priests of the jews could enter and would necessarily be off-limits - by virtue of their own religious fanaticism no less - to the Yahweh purists allowing a small remnant of the cult of Astarte to remain among the jews.
This remnant of the cult - where possibly it had just become part of established ritual as opposed to the few worshippers understanding its original religious purpose - was then what Antiochus IV Epiphanes found upon entering the Holy of Holies: hence the statement that the jews (i.e. their religious leaders) reverenced and worshipped it.
This explanation of events nicely answers two problems with Josephus' testimony and the traditional position take by scholars all at once.
The first problem is why several Greek and Roman writers should have mentioned this and where the idea of a 'golden ass' in the temple of Solomon which the jews worshipped comes from. The issue being simply that we don't have enough evidence to dismiss the Greek and Roman authors unless we trust Josephus' word absolutely, but which we cannot do as Josephus was a highly partisan writer who we know falsified texts when it suited him.
The second problem is why Josephus wrote so furiously against it while Greek and Roman writers so frequently credited it: simply put Josephus was a religious fanatic having taken part and been captured in the first jewish revolt against Rome. So to Josephus any such accusation simply had to be a lie and he did not care as to what evidence could be brought forward in its support: it had to be a lie, because if it was not then everything that Josephus himself believed in would be up for question (and also incidentally destroy Josephus' attempts to prove the great antiquity of Judaism in his ‘Jewish Antiquities’).
While to the Greeks and Romans it was something they had found out from an original source or sources that was then believed by many subsequent writers on the subject of jews: many of whom - like Apollonius Molon - are known to have had a great deal of experience with the jews as a people. Therefore it is unlikely that they would credit so seemingly wild a tale unless they truly believed that on the basis of their experience of the jews this was possible.
We can thus see that the 'Golden Ass in the Temple of Solomon' of legend was quite probably genuine and the jews did indeed worship it.
References
(1) Joseph. Cont. Ap. 2:79-80
(2) S
(3) https://karlradl14.substack.com/p/clearchus-of-soli-aristotle-and-the
(4) Bob Becking, Pieter Willem van der Horst, Karel van der Toorn (Eds.), 1999, 'Dictionary of Deities and Demons in the Bible', 2nd Edition, E. J. Brill: Leiden, pp. 109-110
(5) Cf. William Dever, 2005, 'Did God have a Wife?: Archaeology and Folk Religion in Ancient Israel', 1st Edition, Eerdmanns: Grand Rapids
(6) John Day, 2002, 'Yahweh and the Gods and Goddesses of Canaan', 2nd Edition, Sheffield Academic Press: New York, p. 129