According to 49:2a, Jehovah made the prophet's mouth "like a sharp sword" and also concealed him "in the shadow of His hand."
Jehovah made the prophet a polished arrow and hid him in His quiver (49:2b). The words of the prophet were arrows, and his speaking was the shooting of an arrow.
"He said to me, You are My servant,/Israel, in whom I will be glorified" (v. 3). This indicates that Jehovah considered the prophet as His servant, a part of Israel, for His glorification. Isaiah, Israel, and Christ are all for God's glorification.
The prophet considered himself as laboring in vain, using up his strength for nothing and vanity (v. 4a). Nevertheless, he was assured that the justice due to him was with Jehovah and that his recompense was with his God (v. 4b).
Since Isaiah typifies Christ, the word in verse 4 applies to Christ. People judged Christ wrongly, thinking that His word was nothing and vain. However, Christ was assured that the justice due to Him would come from God. God values Christ's word and will reward Him for His speaking.
The second of the three persons of the servant of Jehovah is Israel (v. 3). Isaiah, the prophet of Jehovah, was a part of Israel; hence, he was one with Israel as the servant of Jehovah. Christ also is a part of Israel (Hosea 11:1; Matt. 2:15b). In the servant mentioned in Isaiah 49:3, Jehovah will be glorified. This typifies that God is glorified in Christ as the Israel of God (John 13:31b).