Jewish Encyclopedia: Hellenism: «Post-exilic Judaism was largely recruited from those returned exiles who regarded it as their chief task to preserve their religion uncontaminated, a task that required the strict separation of the congregation both from all foreign peoples (Ezra x. 11; Neh. ix. 2) and from the Jewish inhabitants of Palestine who did not strictly observe the Law (Ezra vi. 22; Neh. x. 29)».
newadvent.org
Eusebio, Life of Constantine Vol. III Ch. XVIII Life of Constantine (Libro III), Capítulo 18. He speaks of their Unanimity respecting the Feast of Easter, and against the Practice of the Jews.
