Diogenes Laertius Vitae philosophorum 2.8.65

[65] Aristippus was by birth a citizen of Cyrene and, as Aeschines informs us, was drawn to Athens by the fame of Socrates. Having come forward as a lecturer or sophist, as Phanias of Eresus, the Peripatetic, informs us, he was the first of the followers of Socrates to charge fees and to send money to his master. And on one occasion the sum of twenty minae which he had sent was returned to him, Socrates declaring that the supernatural sign would not let him take it; the very offer, in fact, annoyed him. Xenophon was no friend to Aristippus; and for this reason he has made Socrates direct against Aristippus the discourse in which he denounces pleasure. ¹ Not but what Theodorus in his work On Sects abuses him, and so does Plato in the dialogue On the Soul, ² as has been shown elsewhere.