Team Kakashi are stunned to learn that Sai's true mission is to kill Sasuke.  Naruto wants to believe that the smile Sai showed them was real, but there is a possibility that it was all an act.
It said that in a book...
.هذا ما قرأتُه في كتاب
So stand es zumindest im Lehrbuch.
Eso decía en un libro.
Eso decía en un libro.
Il libro diceva così.
Foi isso que eu li em um livro.
Так сказано в книге.