If you wanted to hear what God has to say, how would you go about it? Some people engage in elaborate mystical rituals in an attempt to hear God’s voice. Some go to mediums or prophets or priests who claim to speak on behalf of God. Sometimes God speaks directly through feelings, circumstances or the voice of another person. But mostly God speaks through his Son. As the writer of the Letter to the Hebrews says in the first chapter:
Long ago on many occasions and in various ways God spoke to our ancestors through the prophets, and in these last days he has spoken to us through his Son, the one chosen by him to be heir of everything, and through whom he made the universe. His Son is the reflection of his glory, the representation of his essence, keeping everything going by his powerful commands.
If we want to know what God thinks, we just need to look at Jesus. If someone claims that God has spoken in a particular way, we can verify that claim by checking whether it is consistent with what Jesus said and did. That is one reason why the New Testament is so important; it is our primary way of getting to know what Jesus is like, and the more familiar we become with Jesus the more we are likely to hear when God speaks to us.