Herodotus has documented that the Qedarites were called upon to assist Cambyses II of the Persian empire in his invasion of Egypt in 525 BCE . The Qedarites and Nabataens were known to enjoy close relations , even engaging as wartime allies against the Assyrians . It is possible that the Qedarites were eventually incorporated into the Nabataen state which emerged as the strongest Ishmaelite presence in northwestern Arabia c. the 2nd century CE . In The Cambridge Ancient History , some of the ( Arab ) Nabataens mentioned by Diodorus in his retelling of events that took place in 312 BCE are said to be Qedarites .