This creed was a riff on an ancient cliché, attributed by some to Socrates, others to Thales, that went something like this: “I thank the Fates every day that I was born a Greek, not a barbarian, free, not a slave, and a man, not a woman.” That was how ancient free men defined themselves and their privilege: by their ethnicity (Greek, Roman, etc.), their class (free), and their gender (male).

https://time.com/5410308/early-christian-solidarity/

Hermippus in his Lives refers to Thales the story which is told by some of Socrates, namely, that he used to say there were three blessings for which he was grateful to Fortune: "first, that I was born a human being and not one of the brutes; next, that I was born a man and not a woman; thirdly, a Greek and not a barbarian."

https://en.wikisource.org/wiki/Lives_of_the_Eminent_Philosophers/Book_I