Sodom and Gomorah
"Esaias also crieth concerning Israel, Though the number of the children of Israel be as the sand of the sea, a remnant shall be saved: For he will finish the work, and cut it short in righteousness: because a short work will the Lord make upon the earth. And as Esaias said before, Except the Lord of Sabaoth had left us a seed, we had been as Sodom, and been made like unto Gomorrha." Romans 9:27-29
Israel had become more wicked than Sodom and Gomorrah...
"As I live, saith the Lord GOD, Sodom thy sister hath not done, she nor her daughters, as thou hast done, thou and thy daughters." Ezekiel 16:48
Because of God's promise to the Jewish people, they were not judged like Sodom and Gomorrah...
"For I am the LORD, I change not; therefore ye sons of Jacob are not consumed." Malachi 3:6
"Except the LORD of hosts had left unto us a very small remnant, we should have been as Sodom, and we should have been like unto Gomorrah." Isaiah 1:9
In Romans, God is reaffirming His promise to the Jewish people that He will preserve the Jewish people and rule over them in Israel despite their wickedness.
"And so all Israel shall be saved: as it is written, There shall come out of Sion the Deliverer, and shall turn away ungodliness from Jacob:" Romans 11:26