A.T. Robertson Commentary Galatians 4:26

"But the Jerusalem that is above is free, which is our mother." — Galatians 4:26 (ASV)

The Jerusalem that is above (η ανω Ιερουσαλημ). Paul uses the rabbinical idea that the heavenly Jerusalem corresponds to the one here to illustrate his point without endorsing their ideas. See also Re 21:2. He uses the city of Jerusalem to represent the whole Jewish race (Vincent).