R. Shimon says: When is it derived that if one slaughters the Pesach on a private altar when such altars are forbidden, he is in transgression of a negative commandment? From "You may not sacrifice the Pesach offering in one." I might think (that he transgresses) even when such altars are permitted; it is, therefore, written "in one of your gates" (i.e., You may not do so) when all of Israel are gathered in one place, at which time individual altars are forbidden, and not (i.e., you are not in transgression of the above) when they are permitted.