How beautiful on the mountains
    are the feet of those who bring good news,
who proclaim peace,
    who bring good tidings,
    who proclaim salvation,
who say to Zion,
    ‘Your God reigns!’
8 Listen! Your watchmen lift up their voices;
    together they shout for joy.
When the Lord returns to Zion,
    they will see it with their own eyes.
9 Burst into songs of joy together,
    you ruins of Jerusalem,
for the Lord has comforted his people,
    he has redeemed Jerusalem.
10 The Lord will lay bare his holy arm
    in the sight of all the nations,
and all the ends of the earth will see
    the salvation of our God.

It is significant that Paul quotes Isaiah when writing about the preaching of the gospel:

 How, then, can they call on the one they have not believed in? And how can they believe in the one of whom they have not heard? And how can they hear without someone preaching to them? 15 And how can anyone preach unless they are sent? As it is written: “How beautiful are the feet of those who bring good news!” (Romans 10:14,15).

Preaching the good news of the gospel involves foot and mouth. We ‘bring good news’, which implies movement: going where God sends us. Feet that take the news about Jesus are ‘beautiful’.

I am reminded of Paul writing in Ephesians 6:14,15:

‘Stand firm then, with the belt of truth buckled around your waist, with the breastplate of righteousness in place, 15 and with your feet fitted with the readiness that comes from the gospel of peace.’

Also, earlier in this letter, in 2:17, he says:

‘He came and preached peace to you who were far away and peace to those who were near.’

Paul is describing here how Jesus ‘came’, in and through His church, to preach the message of reconciliation to both Gentiles (who could be described as geographically ‘far away’) and to Jews (‘who were near’). We have again the combination of feet going and a mouth speaking.

The immediate application of the Isaiah passage has to do with the return of the Jews from Babylon to their homeland, and the re-population of Jerusalem (see also 40:9-11). God is going to completely reverse ‘Zion’s’ circumstances and all the world will see Him do it. (Note how in prophecy God sometimes speaks of something that is going to happen as if it had happened. So certain is it. This is known as ‘the prophetic perfect.’ See verses 9,10). However, this is all but a foreshadowing of that greater redemption still to come in and through ‘the Servant of the LORD’, Jesus Christ. So how fitting it is that this passage is to be followed by one in which Isaiah prophesies the suffering and glory of the Messiah.