It's about a letter written by Hephaistion to Olympias.It can be found in Diodorus Siculus Library of history book 17 Chapter 114 § 3
Apparently Hephaistion had received many letters from Olympias where she criticized and threatened him.In that letter he answered her.
We have only the end of the letter but it is only the last sentence which is differently translated in French and in English.The way the text is translated in the 2 languages changes completely the meaning.
French translation : " Tu sais qu'Alexandre est plus puissant que tout le monde" meaning : you know that Alexander is more powerful than anyone else in the world.
English translation : "you know that Alexander means more to us than anything"
What did Hephaistion exactly mean? That he feared nothing because he had the trust of the most powerful man in the world and was under his protection? Or that he didn't care about Olympias' recriminations because all that mattered to him was Alexander? It's 2 different meanings.
Here is the greek text :

English text :
As a matter of fact, Hephaestion enjoyed so much power and freedom of speech based on this friendship that when Olympias was estranged from him because of jealousy and wrote sharp criticisms and threats against him in her letters, he felt strong enough to answer her reproachfully and ended his letter as follows: "Stop quarrelling with us and do not be angry or menacing. If you persist, we shall not be much disturbed. You know that Alexander means more to us than anything."