Yahweh is talking about Judah and Israel.

## The leaders of Judah are like those who move a boundary stone. ##

Moving a boundary stone meant moving the landmark that marked the border of some property (which was a crime under Israelite law).  (See: [[rc://en/ta/man/translate/figs-simile]])

## I will pour my wrath on them like water. ##

Yahweh's wrath against Judah will be like a very large stream of water that destroys them. (See: [[rc://en/ta/man/translate/figs-simile]])

## Ephraim is crushed; he is crushed in judgment ##

This statement is made twice for emphasis: Ephraim's punishment will be very harsh; Ephraim's judgment for following idols will be severe. The second statement emphasizes the severity of the judgment.