OK, the title is opinionated and contentious, but I have a definite
question. I know that the title refers to the Bourbaki volume
*Groupes et Algèbres de Lie* (Chapters 4-6), published in 1968, but

>who said that it is the only great book that Bourbaki ever wrote?

The only reference I can find is the 2009 Prize Booklet for the AMS-MAA
Joint Meetings, where no source is given, but I'm sure I've seen the
claim somewhere else.

**Edit.** I have rolled back the title of this question to its original
form, because putting the title in quotes misled some people into thinking
I sought a source for the exact phrase "the only great book that Bourbaki
ever wrote." Rather, I wanted a source (not necessarily unique) for the *idea*
that Chapters 4-6 of *Groupes et Algèbres de Lie*  is Bourbaki's one great
book. Gerald's answer and Jim's comment together are exactly what I wanted.