Panta rhei, “everything flows" 
Πάντα ῥεῖ (panta rhei) "everything flows” either was not spoken by Heraclitus or did not survive as a quotation of his. This famous aphorism used to characterize Heraclitus’ thought comes from Simplicius, a neoplatonist, and from Plato’s Cratylus. The word rhei (cf. rheology) is the Greek word for “to stream, and to the etymology of Rhea according to Plato’s Cratylus.”
The philosophy of Heraclitus is summed up in his cryptic utterance:
ποταμοῖσι τοῖσιν αὐτοῖσιν ἐμϐαίνουσιν, ἕτερα καὶ ἕτερα ὕδατα ἐπιρρεῖ.
Potamoisi toisin autoisin embainousin, hetera kai hetera hudata epirrei
“Ever-newer waters flow on those who step into the same rivers.”
τὰ ὄντα ἰέναι τε πάντα καὶ μένειν οὐδέν”
Ta onta ienai te panta kai menein ouden
“All entities move and nothing remains still”
and in 402,a
“πάντα χωρεῖ καὶ οὐδὲν μένει” καὶ “δὶς ἐς τὸν αὐτὸν ποταμὸν οὐκ ἂν ἐμβαίης”
Panta chōrei kai ouden menei kai dis es ton auton potamon ouk an embaies
“Everything changes and nothing remains still … and … you cannot step twice into the same stream”
Instead of “flow” Plato uses chōrei, to change chōros.
The assertions of flow are coupled in many fragments with the enigmatic river image:
Ποταμοῖς τοῖς αὐτοῖς ἐμβαίνομέν τε καὶ οὐκ ἐμβαίνομεν, εἶμέν τε καὶ οὐκ εἶμεν.
“We both step and do not step in the same rivers. We are and are not.”
Compare with the Latin adages Omnia mutantur and Tempora mutantur (8 CE) and the Japanese tale Hōjōki, (1200 CE) which contains the same image of the changing river, and the central Buddhist doctrine of impermanence.