Changes in Resh Pronunciation
In Hebrew, the classical pronunciation associated with the consonant ר rêš was flapped, and was grammatically treated as an ungeminable phoneme of the language. In most dialects of Hebrew among the Jewish diaspora, it remained a flap or a trill . However, in some Ashkenazi dialects as preserved among Jews in northern Europe it was a uvular rhotic, either a trill or a fricative . This was because many (but not all) native dialects of Yiddish were spoken that way, and their liturgical Hebrew carried the same pronunciation. Some Iraqi Jews also pronounce rêš as a guttural, reflecting their dialect of Arabic.
An apparently unrelated uvular rhotic is believed to have appeared in the Tiberian vocalization of Hebrew, where it is believed to have coexisted with additional non-guttural articulations of /r/ depending on circumstances.
Read more about this topic: Modern Hebrew, Phonology