Stobaeus 3.17.23, in Ioannis Stobaei Anthologium
, Vol. III, ed. Otto Hense (Berlin: Weidmann, 1894), p. 495 (my translation, adopting Usener's restoration):
If you want to make Pythocles rich, don't add to his possessions, but take away from his desire.
εἰ βούλει πλούσιον τινα ποιῆσαι, μὴ χρημάτων προστίθει, τῆς δὲ ἐπιθυμίας ἀφαίρει.
Πυθοκλέα pro τινα Epicuro reddidit Vsener duce Annaeo
Cf. Stobaeus 3.17.36, in Ioannis Stobaei Anthologium
, Vol. III, ed. Otto Hense (Berlin: Weidmann, 1894), p. 502 (my translation):
Epicurus, when asked how someone might become rich, said, "Not by adding to his possessions, but by cutting away most of his wants."
Ἐπίκουρος ἐρωτηθείς πῶς ἄν τις πλουτήσειεν, 'οὐ τοῖς οῦσι προστιθείς' ἔφη 'τῆς δὲ χρείας τὰ πολλὰ περιτέμνων'.
Seneca, Letters to Lucilius
21.7 (tr. Richard M. Gummere):
In order that Idomeneus may not be introduced free of charge into my letter, he shall make up the indebtedness from his own account. It was to him that Epicurus addressed the well-known saying, urging him to make Pythocles rich, but not rich in the vulgar and equivocal way. "If you wish," said he, "to make Pythocles rich, do not add to his store of money, but subtract from his desires."
ne gratis Idomeneus in epistulam meam venerit, ipse eam de suo redimet. ad hunc Epicurus illam nobilem sententiam scripsit, qua hortatur, ut Pythoclea locupletem non publica nec ancipiti via faciat. "si vis," inquit, "Pythoclea divitem facere, non pecuniae adiciendum, sed cupiditati detrahendum est."
The citations come from Hermann Usener, Epicurea
(Leipzig: B.G. Teubner, 1887), pp. 142-143, although Usener incorrectly cites Stobaeus 3.17.37 ("idem XVII 37," should be 36) for the second quotation.