# your people, Israel, are

"your people, O Israel, are" 

# are like the sand of the seashore

"are too many to count, like the sand on the seashore" 

# Destruction is decreed

"Yahweh has decreed that he will destroy most of those who live in Israel"

# as overflowing righteousness demands

"This must be done for the sake of perfect righteousness" or "Yahweh must do this because he is completely righteous"