In Season 2 Episode 1 just befor John dies he whispers something to Dean. Does anyone know what it is or when you find out?

You find out in episode 2x10, "Hunted" what John whispered to Dean.

*****SPOILER ALERT***** Read no further if you don't want to know what he said!!!!!!!


John told Dean that if he couldn't save Sam from going darkside, that he might have to kill him. It was a real shocker!!

**Edit** Okay, I'm going to update my answer! :)

Ep 2x10, Hunted:

Dean: Before Dad died he - he told me something, something about you.
Sam: What? Dean, what did he tell you?
Dean: He sinabi that he wanted me to watch out for you, to take care of you.
Sam: He told you that a million times.
Dean: No, this time was different. He sinabi that I had to save you.
Sam: Save me from what?
Dean: He just sinabi that I had to save you, that nothing else mattered, and that if I couldn't I'd...
Sam: You'd what Dean?
Dean: That I'd have to kill you. He sinabi that I might have to kill you, Sammy!
Sam: Kill me? What the hell is that supposed to mean?
Dean: I don't know.
Sam: I mean, he must have had some kind of reason for saying it, right? Did he know the demon's plans for me? Am I supposed to go darkside or something? What else did he say, Dean?
Dean: Nothing, that's it, I swear.
:))

John tells Dean he has to save Sam and if he is not able to ,he will have to kill him.

john whispers in dean ear that sam is very dangerous and that the y.e.d had did something to him and that one araw dean would have to kill sam one day. you will find out what has happened in season 2 episode 9 and 10

he tells dean if he cant save sammy hell have to kill him

John whispers to dean " You might have to kill Sammy".

John Winchester tells Dean that Sam has Demon blood in him and that Dean may have to kill Sam

To watch out for Sam, because he may have to kill him.

To kill Sam

Either save Sammy or kill him.

some araw you might have to kill your brother

John told Dean that he might have to kill Sam

That if Dean can't save Sam, than he'd have to kill him.
Dean: Before Dad died, he told me something. Something about you.
Sam: What? Dean, what did he tell you?
Dean: He sinabi if I can't save you, than I'd have to kill you Sammy.

Dean watch out for Sam you must save him or kill him

That Sam might turn evil and if that happens dean has to kill him.

DEAN: Before dad died, he... he told me somethin'. Somethin' about you.
SAM: What? Dean, what did he tell you?
DEAN: He sinabi that he... wanted me to watch out for you. Take care of you.
SAM: He told you that a million times.
DEAN: [shakes head] This time was different. He sinabi that I had to... save you.
SAM: Save me from what?
DEAN: He just sinabi that I have to save you, that nothing else mattered, and that if I couldn't, I'd...
SAM: You'd what, Dean?
DEAN: I'd have to kill you. He sinabi that I mighT have to kill you.
So yeah that's what it is.

Sam dies

We never actually heard it until Dean confessed to Sam and it was for him to watch out for his little brother.

Ouyuyvyug