Christians, who is this man mentioned in the verse?

the first passage you mention in Isaiah 42 is about Jesus Christ. The Good News of Jesus Christ spread to Arabia that is why they can rejoice. The Bible clearly teaches that Jesus Christ is God, not just a prophet. The Bible says that Jesus is God: Hebrews 1:8, Titus 2:13, John 1:1, Colossians 2:9, John 8:58, Isaiah 9:6.