Romans 2:24 — For the name of God is blasphemed among the Gentiles through you, as it is written.
The Jews' lifestyle made Gentiles speak out against God. The as it was written is a reference to …
Isaiah 52:5 — Now therefore, what have I here, saith the LORD, that My people is taken away for nought? they that rule over them make them to howl, saith the LORD; and My name continually every day is blasphemed.
Also Ezekiel 36:16-20 — Moreover the word of the LORD came unto me, saying, son of man, when the house of Israel dwelt in their own land, they defiled it by their own way and by their doings: their way was before Me as the uncleanness of a removed woman. Wherefore I poured My fury upon them for the blood that they had shed upon the land, and for their idols wherewith they had polluted it: and I scattered them among the heathen, and they were dispersed through the countries: according to their way and according to their doings I judged them. And when they entered unto the heathen, whither they went, they profaned My holy name, when they said to them, These are the people of the LORD, and are gone forth out of His land.