Isaiah 40:9 (ESV) … “Go on up to a high mountain, O Zion, herald of good news; lift up your voice with strength, O Jerusalem, herald of good news; lift it up, fear not; say to the cities of Judah, “Behold your God!”
It is amazing just how often one still finds people who think that the gospel is to be found only in the New Testament. Those who do most likely have never read Isaiah! In fact, the first gospel promise is found in Genesis 3, immediately after the Fall, when God promises Eve that her seed will be the means of conquering Satan and his kingdom forever (Gen. 3:15).
Isaiah is asked to proclaim the same message in effect. It is ‘tidings’, or news that is to be proclaimed from the ‘high mountain’ and ‘with a shout’. This is a message worth getting excited about. And what is the message? Quite simply, ‘Behold your God!’ Old Testament believers were to be witnesses to the gospel. ‘You who bring good tidings’ (40:9) is one word in the Hebrew. Its Greek equivalent is ‘evangelist’. Evangelism is speaking to others about God: what he is like, what he threatens to do, what he promises to those who love his Son.
The Bible never proves the existence of God. You can search from Genesis to Revelation and what you find on every page is the assumption that God exists, and that men know that he exists. When Paul preaches to the philosophers at Athens, he takes it for granted that they believe in God. ‘God has endued all men with some sense of his godhead’, with the result that ‘a sense of deity is inscribed on every heart.’ What the Athenians needed to know was the nature of God. What Paul did on the Areopagus was to expound on the attributes of God: elaborating in turn upon God as Creator, Sustainer Ruler, Father and Judge.
That is exactly what Isaiah is going to do: preach to the people of Judah about the character of God. He is describing God’s attributes in detail. He confronts us with the only God there is and call upon us to make peace with Him.