Diodorus of Sicily: Greek historian, author of the Library of World History. His activities can be dated between 60 and 30 BCE.
In April 323, Alexander the Great entered Babylon. The Chaldaeans, i.e., the famous astrologers working in the Esagila temple complex, came with warnings that he would die if he entered the city without due precautions.
Diodorus of Sicily describes this his World History, section 17.112. They are given here in the translation by C. Bradford Welles.
Alexander and the Chaldaeans
[17.112.1] After the conclusion of his war with the Cossaeans,note[A mountain tribe south of Ecbatana, in modern Luristan.] Alexander set his army in motion and marched towards Babylon in easy stages, interrupting the march frequently and resting the army.
[17.112.2] While he was still 54 kilometers from the city, the scholars called Chaldaeans, who have gained a great reputation in astrology and are accustomed to predict future events by a method based on age-long observations,note[This is a correct description of the practice of the astronomers of Babylon.] chose from their number the eldest and most experienced. By the configuration of the stars they had learned of the coming death of the king in Babylon, and they instructed their representatives to report to the king the danger which threatened. They told their envoys also to urge upon the king that he must under no circumstances make his entry into the city;
[17.112.3] that he could escape the danger if he re-erected the tomb of Belusnote[The tomb of Belus (= Bêl = the Babylonian supreme god Marduk) is better known as the "tower of Babel", i.e. the temple tower Etemenanki in the center of Babylon.] which had been demolished by the Persians, but he must abandon his intended route and pass the city by.
The leader of the Chaldaean envoys, whose name was Belephantes,note[His real name was Bêl-apla-iddin.] was not bold enough to address the king directly but secured a private audience with Nearchus, one of Alexander's friends, and told him everything in detail, requesting him to make it known to the king.
[17.112.4] When Alexander, accordingly, learned from Nearchus about the Chaldaeans' prophecy, he was alarmed and more and more disturbed, the more he reflected upon the ability and high reputation of these people. After some hesitation, he sent most of his friends into Babylon, but altered his own route so as to avoid the city and set up his headquarters in a camp at a distance of 36 kilometers.
This act caused general astonishment and many of the Greeks came to see him, notably among the philosopher Anaxarchus.note[Anaxarchus (c.380-320) was a followers of the doctrine of Democritus of Abdera, who believed that everything was made up from atoms and often denied divine interventions in human life. It is possible, however, that Anaxarchus was (later) convinced of the truth of the prediction, because he is known to have said to Alexander that "a god would be struck by a human" (Diogenes Laertius, Lives of the philosophers 9.60; Euripides, Orestes 271).]
[17.112.5] When they discovered the reason for his action, they plied him with arguments drawn from philosophy and changed him to the degree that he came to despise all prophetic arts, and especially that which was held in high regard by the Chaldaeans. It was as if the king had been wounded in his soul and then healed by the words of the philosophers, so that he now entered Babylon with his army.
[17.112.6] As on the previous occasion,note[I.e., when Alexander visited the city in the last months of 331.] the population received the troops hospitably, and all turned their attention to relaxation and pleasure, since everything necessary was available in profusion.