What does Ezekiel 47:19 mean?

The southern border starts at Tamar and runs along the waters of Meribah Kadesh, then follows the river to the Mediterranean Sea. That’s your southern border. Ezekiel 47:19 - Modern Text Bible

(The southern edge is defined by a route from Tamar, past a famous spring, and out to the sea. It’s marking the bottom edge of the land.)