Attributed to Heraclitus
«No man ever steps in the same river twice, for it is not the same river and he is not the same man.»
Misattributed
Verdict
It is not in Heraclitus's work
A modern expansion combining B12, B91 and the disputed B49a ("we step and do not step into the same rivers, we are and are not"). The second half, about the man no longer being the same, is in no ancient source.
What they did say
Verified words of Heraclitus
«Though this Word is true evermore, yet men are as unable to understand it when they hear it for the first time as before they have heard it at all. For, though all things come to pass in accordance with this Word, men seem as if they had no experience of them, when they make trial of words and deeds such as I set forth, dividing each thing according to its nature and showing how it truly is. But other men know not what they are doing when awake, even as they forget what they do in sleep.»
DK 22 B1, transmitido por Sexto Empírico, Contra los matemáticos VII 132; Aristóteles (Retórica III 5) lo cita como comienzo del libro. Griego: Diels-Kranz; inglés: John Burnet, Early Greek Philosophy (1908), fr. 2 de la numeración de Bywater; español: traducción propia.
«It is wise to hearken, not to me, but to my Word, and to confess that all things are one.»
DK 22 B50, en Hipólito, Refutación de todas las herejías IX 9.1. Griego: Diels-Kranz; inglés: John Burnet, Early Greek Philosophy (1908), fr. 1 de la numeración de Bywater; español: traducción propia.
«This world, which is the same for all, no one of gods or men has made; but it was ever, is now, and ever shall be an ever-living Fire, with measures kindling, and measures going out.»
DK 22 B30, en Clemente de Alejandría, Stromata V 104.2. Griego: Diels-Kranz; inglés: John Burnet, Early Greek Philosophy (1908), fr. 20 de la numeración de Bywater; español: traducción propia.