Romans 2:24

‘For the name of God is blasphemed among the Gentiles because of you, even as it is written.'

Indeed he declares that as a result of their activity the name of God is blasphemed among the Gentiles, and claims Scriptural support, without citing it. It may be that he had in mind Isaiah 52:5, ‘those who rule over them howl, says the Lord, and my Name is continually blasphemed all the day'. The Scripture might be seen as not applying directly for it has in mind that what causes the Lord's name to be blasphemed among the Gentiles is that His people are ruled there by foreign rulers who intimidate them, but Paul's point was probably simply that it was an instance of how His people could cause His name to be blasphemed among the Gentiles. He could also have argued that they were actually where they were under foreign rulers because of their sins. The lack of direct parallel would explain why he does not cite it directly.

Because of the difficulty with the parallel some have suggested that Paul had in mind Ezekiel 36:20, ‘ and when they came to the nations to which they went they profaned my holy Name in that men said of them, “These are the people of the LORD and they are gone forth from the land”.' But that falls at a similar hurdle of not being directly appropriate, and the Isaiah reference is much closer linguistically.