Many popular histories contain the following phrase, or a variant on it:
"I, Philip Kearny, an old soldier, enter my solemn protest against this order for retreat,- we ought, instead of retreating, to follow up the enemy and take Richmond. And in full view of all the responsibility for such a declaration, I say to you all, such an order can only be prompted by cowardice or treason."
I say variant because this is the original form that appeared, and no author I can find has referenced the original source since 1944. The original of this statement is in Rev J.J. Mark's "The Peninsula Campaign in Virginia" (page 294). This is an interesting work in its own right and deserves to be read (more later). Modern authors do not use the original source; McPherson in his "Battle Cry of Freedom" references Catton's "Mr Lincoln's Army", whilst altering the form of the statement slightly. Catton references Kearny's grandson's work on his grandfather, which was reviewed that "the work as a whole must be dismissed as lengthy family glorification" (ref). Thomas Kearny so objected to the review that he sued (ref). Sears in his "To the Gates of Richmond" alters the quote (although not materially) and does not reference it. The current keepers of the wikipedia page on Kearny not only alter the quote and fail to reference it, but insist he actually wrote it.
Apparently in the 1860's there was considerable controversy about whether Kearny had actually uttered these words, as John Watts de Peyser actually comments on it dismissing such claims (ref). In the 1860's the quote was used to criticise Kearny for "over-rashness" (while admitting McClellan's "over-caution"), since it is plainly obvious that Kearny is actually wrong (ref).
On of the major problems with Rev. Marks' story was that he wasn't there. He had volunteered to remain behind with the field hospital when McClellan began his change of base and had to abandon them. He never actually returned to his unit, going to Libby Prison with the wounded, and resigning his Commission upon return to the north. This was pointed out and Marks replied it was confirmed by an (unnamed) "officer of high rank".
I've no idea whether Kearny said the above or not. It seems in keeping with his character certainly. I do however object to the fact that everyone references Catton, who is not using the statement in its' original form.