“Look!” The Greek word is idou (#2400 ἰδού), and it is used to get our attention. See commentary on Matthew 1:20.
“my servant.” Matthew 12:18-21 are quoted from Isaiah 42:1-4 and are the first four verses of the first “Servant Song” in Isaiah (called a “song” because Isaiah wrote in Hebrew poetry). The “Servant Songs” are sections of Isaiah that are about the Messiah, Jesus Christ, and present him as the Servant of God. The four “Servant songs” are: Isaiah 42:1-7; 49:1-7; 50:4-11; 52:13-53:12. The last Servant song is familiar to us because of Isaiah 53, but few people realize the song starts in chapter 52, and unfortunately is broken up by the chapter break of Isaiah 53. The chapter breaks were added to the Old Testament in the thirteenth century AD, some 2,000 years after Isaiah wrote, and the song would have been much easier to see and understand had it not been interrupted by the chapter break.
The fact that Matthew 12:17 says that Jesus fulfilled the Servant Song shows conclusively that Jesus is the “servant” of the Servant songs in Isaiah. The disciples understood this also because in Acts 4:27 they prayed to God and referred to Jesus as “your holy servant Jesus, whom you anointed.” This is likely an allusion to Isaiah 42:1, which speaks of Jesus as the Servant of God and that he was given (thus “anointed with”) the holy spirit by God.
The Servant Songs are sections of Isaiah that are specifically about the Messiah, and would have enabled Jesus to more clearly understand his mission and what he would have to endure to accomplish it.
“my soul.” The Greek word often translated “soul” is psuchē (#5590 ψυχή; pronounced psoo-'kay), and it has a large number of meanings, including the physical life of a person or animal; an individual person; or attitudes, emotions, feelings, and thoughts. We can tell that in this verse “my soul” is equivalent to “me” (including my thoughts, emotions, and feelings) because the “my” is God, and He is not a body powered by soul.
[For a more complete explanation of “soul,” see Appendix 7, “Usages of ‘Soul.’”]