The Lord did not cease being holy when the New Testament began; his nature did not change. If we would know him as he is, we need an old testament fear of God combined with a New Testament experience of his Grace.
After Solomon dedicated the temple, the glory of the lord descended and filled his house (II Chronicles 7:1-3). What was this glory? It was the light breaking forth upon humanity. It signified the Lord's actual person had drawn near!
The Hebrew people knew God was holy. Yet he was too holy for them to face as sinful individuals. They served him without relating to him. Today, as Christians, through the blood of Jesus, God has opened the way for us to enter the holy place of his presence (Hebrews 10:19-22).
Be careful, many Christians celebrate the forgiveness of sins in Christ, but end their experience on that level. Jews still fear God, but lived outside his divine presence because they did not understand the forgiveness of sins in Christ.
It is the union of both truths which produces the power of understanding in our lives and leads us into the presence of God.