The lines presented below are from the
Chess Informant ECO 1984, but I doubt the assessments have changed since:
[White "Sicilian defense"]
[Black "Najdorf variation"]
1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.Bg5 e5?! 7.Bxf6 Qxf6 ( 7...gxf6 8.Nb3 f5 9.Qh5+/- ) 8.Nd5 Qd8 9.Nf5 Bxf5 ( 9...Be6 10.Bc4 Nd7 11.O-O Rc8 12.Bb3 Nc5 13.Qf3 Nxb3 14.Qxb3 Rc5 15.Rad1 Rb5 16.Qg3!+/- ) 10.exf5 Be7 11.c4+/-
Although my edition of the
ECO is old, I doubt anything has changed here.
In the main line Black has no counter-play-his only plan of attack-
b5 is useless as White will take with the bishop thus eliminating every Black's counter-play.
White has strong grip on the light squares, and presence of the bishops of the opposite color increases his advantage-remember this rule:
Presence of the opposite colored bishops favors the side with the initiative. Although they may end up as a draw in the endgame, in the middle-game side that has an attack usually wins.
In the first sideline, Black tried to generate some counter-play with
f5 but White's
Qh5 keeps advantage. If Black continues with passive play then White keeps advantage due to the initiative and presence of the opposite colored bishops.
Black's last sideline features
Be6 trying to ignore Whites plan, but we see that White develops strong pressure again.
I am not an
1.e4 player, so I was unable to find more concrete lines but these illustrate well enough why
e5 is dubious move for Black. If you need better coverage then try to find some repertoire books-at this point I can not recommend any.