One day, God's generous salvation will reach beyond Israel and Judah. This will lead nations to come to Zion, not for war, but to receive blessings and live by God's rules.
Isaiah urged Judah to see the benefits that other nations would gain. He wanted to inspire the people of Judah (Isaiah 2:5) to feel motivated and follow the Lord, so they would not miss out on that day.
This section is almost exactly repeated in Micah 4:1–3.