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

(Referenties: Apocalypse Explained 850)

The Lord, in the simplest terms, is love itself expressed as wisdom itself. In philosophic terms, love is the Lord's substance and wisdom is His form. Of course, we feel the Lord's love and hear His wisdom in many different ways, depending on our state in life and how receptive we are. That's why the Lord has so many different names in the Bible, and is referred to in so many different ways.