Besides what his allah said in Quran 9:30, Muhammad himself stated that on the Day of Resurrection, "the Jews would be summoned, and it would be said to them: What did you worship? They will say: We worshipped 'Uzair [Ezra], son of Allah. It would be said to them: You tell a lie; iAllah had never had a spouse or a son." (Sahih Muslim, book 1, Hadith 352).
Jews knowledgeable about their scriptures would tell you that in the Old Testament, in the 7th Chapter of Ezra, first verse, it is recorded that Ezra is the son of Seraiah [not God!].
Like Muslims, Jews believe that the god of the universe has no son: From the Jewish holy text Exodus Rabbah 29 we read about God: "I am the first, I have no father; I am the last, I have no brother. Beside Me there is no God; I have no son."