Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[80] DEMETRIUS being thus slain in battle, as we have above related, Alexander took the kingdom of Syria; and wrote to Ptolemy Philometor, and desired his daughter in marriage; and said it was but just that he should be joined an affinity to one that had now received the principality of his forefathers, and had been promoted to it by God's providence, and had conquered Demetrius, and that was on other accounts not unworthy of being related to him. Ptolemy received this proposal of marriage gladly; and wrote him an answer, saluting him on account of his having received the principality of his forefathers; and promising him that he would give him his daughter in marriage; and assured him that he was coming to meet him at Ptolemais, and desired that he would there meet him, for that he would accompany her from Egypt so far, and would there marry his child to him. When Ptolemy had written thus, he came suddenly to Ptolemais, and brought his daughter Cleopatra along with him; and as he found Alexander there before him, as he desired him to come, he gave him his child in marriage, and for her portion gave her as much silver and gold as became such a king to give.