In his eighteenth year he became rabbi of Uskup, in present-day Republic of North Macedonia (Üsküp - Ottoman Turkish: اسكوب).
In 1708 he made his appearance in Smyrna, where he won some adherents willing to help him publish his Mehemnuta de Kulla, and thus secure a rabbinical position for him.
In Venice, however (1711), with the approval of the rabbis of that community, he had printed an extract from his work, under the title Raza di-Yiḥudah, into the beginning of which he had woven the first stanza of a lascivious Italian love-song, La Bella Margaritha, with a mystical hymn entitled Keter 'Elyon.
Almost from the outset he encountered the antagonism of Tzvi Ashkenazi, rabbi of the German congregation of Amsterdam, who mistook him for another Ḥayyun, an old enemy of his.
Distrusting their own rabbi, Solomon Ayllon, this board brought the matter before Tzvi Ashkenazi, who, of course, very soon detected its heretical character and called for its author's expulsion.
Without awaiting the decision of this commission, Tzvi Ashkenazi and his anti-Shabbethaian friend Moses Hagiz excommunicated Ḥayyun (July 23, 1713).
In spite of the objections of two members of the commission, one of them Ayllon's own son, they declared Ḥayyun entirely guiltless of heresy, and he was rehabilitated in a solemn assembly of the great Amsterdam synagogue.
But Ḥayyun was excommunicated by many other outside congregations, and his disreputable antecedents and the deceptive means by which he acquired introductions were exposed, especially by Leon Brieli, the aged rabbi of Mantua.
In spite of this the members of the Portuguese commission adhered to their decision, but felt themselves bound to publicly exonerate themselves, and for this purpose issued Ḳoshṭ Imre Emet, a pamphlet which was not without obvious misstatements.
In August 1724, through the influence of a vizier, he succeeded at Constantinople in absolving himself from the excommunication on the condition that he should abstain from teaching, writing, and preaching on cabalistic subjects.