He belonged to a family of rabbis in Ostrowo, where his father, Isaac Cohen, a great-great-grandson of the Judah Loew ben Bezalel, had fled during the Polish–Cossack–Tatar War.

The Shabbethaian cabalist Nehemiah Hayyun appeared in Prague, declaring himself a preacher or an emissary from Palestine, and by his duplicity gained the confidence of the credulous Cohen.

It is not astonishing, therefore, that when Ḥayyun asked for an approbation for his mystical work Mehemnuta de Kula, Cohen, to whom he had prudently submitted only the main text, but not the commentaries which accompanied it, and in which the author openly professed the doctrine of the Trinity, readily granted it, and gave him a glowing recommendation.

It was in 1713, while Cohen was staying at Breslau (where he acted as a rabbi until 1716), that Ḥakam Ẓebi Ashkenazi of Amsterdam informed him of its tenets.

[1] In 1715 Cohen went to see August II, King of Poland, to secure reinstatement in his former rabbinate of Posen, at that time vacant; but failed because of the opposition of the leaders of the community.