Quote from : Buffy the Vampire Slayer, Vol. 1 Book

Boys", Buffy hissed through clenched teeth, "being quiet is an important part of sneaking." "Oh, sorry", Xander said, reducing his voice to a whisper. "Besides, ritual sacrifice is a religious rite", Giles went on quietly. "They wouldn't sacrifice just anyone at random. It's far more likely they'd suspect you of being a Roman spy scouting for the invasion and just outright kill you". "Oh great! Great! Way to be encouraging Giles. And I suppose you'll just watch that happen, in your Watchery way.