Does God change between the Old and New Testaments?
No, God does not change between the Old and New Testaments. The same God is present in both, and He has never changed from eternity past nor will He into eternity future. Only His responsibilities placed on the human race change.
Les explains that even though Matthew's genealogy is set in the Jewish economy under the Law, it is the same God. He points to Romans 5:20 as helping explain this, saying God has not changed from eternity past and never will into eternity future. The only change is the responsibilities God assigns to the human race. The inclusion of Tamar, Rahab, and Ruth shows Gentiles and taboo peoples in the genealogy, yet God remains the same.