Amos 5:4

⁴ For thus saith Jehovah unto the house of Israel: Seek ye me, and ye shall live.

Hosea 4:15

¹⁵ Though thou, Israel, play the harlot, let not Judah trespass; and come ye not unto Gilgal, neither go up to Beth-aven, nor swear [As] Jehovah liveth!

The 'city of Judah,' as in Isaiah 40:9, signifies the doctrine of love towards the Lord and love towards our neighbor.