Sforno on Genesis 37:6/ספורנו על בראשית ל״ז:ו׳

1שמעו נא החלום הזה, not only did he tell them his dream, as something by the way, but he invited them to listen to him tell it by saying שמעו נא “please pay attention!” This could not fail to intensify the hostility of his brothers, as we see immediately by their reaction: “do you plan to rule over us?!”