Romans 10:18

‘But I say, “Did they not hear?” Yes, truly, “Their sound went out into all the earth, and their words to the ends of the world.”

Paul then asks the question as to whether in fact the Messianic message has not been heard (in order to emphasise that it has been). He is no doubt referring to an objection put by some that men had not heard the message. His reply is put in Scriptural terminology, (but not necessarily as providing an authoritative citation, for it has no introductory ‘it is written' or equivalent). Here he has in mind how the Gospel has spread widely, ‘into all the earth', although that is not to be taken in terms of what we would call ‘worldwide'. This is evident from Romans 1:8 where Paul could say of the Roman Christians that ‘their faith was spoken of throughout the whole world' (Romans 1:8), that is, was spoken throughout the wide area that the Gospel had reached. He was, in fact, referring to Christians who would have knowledge about the Roman church, Christians in his ‘world'. He was speaking of the world as he knew it. Compare also how Jews were gathered in Jerusalem at Pentecost from ‘every nation under Heaven' (Acts 2:5), in other words from all around their known world.

The final sentence in the verse (18b) comes from Psalms 19:4, but he does not present it as a Scripture citation. Rather he appropriates the words as being convenient for the purpose of expressing what he wants to say, which is that the word of the messengers of the Messiah has reached the world as it was known to him. He sees the words as an indication of God's mind, that all should hear, both Jew and Gentile.