323 BCE, Following the death of Alexander, Ptolemy established himself as satrap of Egypt.
Ptolemy, one of the late Alexander’s generals wasted no time in establishing himself in Egypt. Not yet proclaimed a king, he made use of his fertile and easily defendable province to position himself in opposition to Perdiccas, the regent acting on behalf of the infant Alexander IV.
Diodorus Siculus, The Library of History, 18.14.1-2 In Asia, of those who had shared in the division of the satrapies, Ptolemy took over Egypt without difficulty and was treating the inhabitants with kindness. Finding eight thousand talents in the treasury, he began to collect mercenaries and to form an army. A multitude of friends also gathered about him on account of his fairness. 2 With Antipater he carried on a diplomatic correspondence that led to a treaty of co‑operation, since he well knew that Perdiccas would attempt to wrest from him the satrapy of Egypt.[1]
Flavius Josephus, Antiquities of the Jews 12.11 When Alexander had reigned twelve years, and after him Ptolemy Soter forty years, Philadelphus then took the kingdom of Egypt, and held it forty years within one. He procured the law to be interpreted, and set free those that were come from Jerusalem into Egypt, and were in slavery there, who were a hundred and twenty thousand.[2]
[1] Diodorus Siculus, The Library of History, 18.14.1-2.
[2] Flavius Josephus, Antiquities of the Jews, 12.11.