Carrying A Weapon On Shabbos

A man should not go out with a sword, a bow, an alloh [round shield], or a spear. And if he did go out, he is liable for a sin offering. Rabbi Eliezer says: they are ornaments for him! But the Sages say: they are nothing but dishonorable, as it is said: "And they shall beat their swords into plowshares and their spears into pruninghooks: national shall not lift up sword against nation, neither shall they learn war any more."

(Mishnah - Shabbos 6:4)