Micah 1:9

Samaria had a wound from which she could not recover, namely, a wound of punishment caused by her sin (cf. 1 Kings 20:21). This sin and its consequence had also infected Judah, even the capital city of Jerusalem (cf. Isaiah 1:5-6). Jerusalem should have been especially holy because of the temple and God’s presence there, but it was polluted. Punishment reached the gate of Jerusalem in 701 B.C. when Sennacherib attacked the city, but the Lord turned back the invader (cf. 2 Kings 18-19).

"The problem with Samaria was that she was toxic; her infection had spread to Judah." [Note: Warren W. Wiersbe, "Micah," in The Bible Exposition Commentary/Prophets, p. 391.]