Sam, Loyal friend, bravest hobbit, or just scared

[akhtene]

he made no promise to anyone to bind him to frodo.

I don't remember how it was in the film, and in the book Gandalf needs no promises: he just states how it's going to be: "You shall go away with Mr Frodo.

But the promise was really given, to Gildor; and quite an eloquent promise it was. (ch. 'A Short Cut to Mushrooms')