Their request cannot be honored until they agree to join with the rest of their compatriots in the war of conquest. If we turn back a few chapters to the portion of Hukat, we discover the theme of human speech standing in direct confrontation with a physical act of striking. Soon after the death of Miriam, the Israelites complain about the lack of water, leading G-d to instruct Moses to speak to the rock after which it will yield a supply of water. Moses, however, has exhausted his tolerance for the nation's constant whining. Instead of addressing the rock with words, he hits the rock with strength, not only once but twice.
Water does emerge, enough for the entire nation.
Perhaps the reason is because the mission of the Israelites was to amplify the power of the word, of speech, of the book, of Torah. The rock which was Rome, the rock which was Babylon, the rock which was Egypt - all these have turned to dust over the ages. Nothing of their once proud civilizations is left except for archeological sites. But the word, the message of G-d as preserved in the Torah by the Jewish People, is a living reality, giving shape to people's lives throughout the world. The sword is a symbol of Gentiles.