Jesus IS the Messiah because He is the Word.

Yes. Everybody has sinned except Jesus. He literally lived by the Word of God because He IS the Word of God (i.e., God); it was in Him from the moment of conception in the womb without physical contact.

• And the angel answered and said unto her, The Holy Ghost shall come upon thee, and the power of the Highest shall overshadow thee: therefore also that holy thing which shall be born of thee shall be called the Son of God. Luke 1:35.

The Father placed His Word inside a human when He conceived His begotten son by the Holy Ghost, the Spirit of Truth. Jesus is "God with us," Emmanuel, the Messiah, because of the Word in Him.

• Behold, a virgin shall be with child, and shall bring forth a son, and they shall call his name Emmanuel, which being interpreted is, God with us. Matthew 1:2

The begotten son, Jesus, became the servant of the Father on earth. Remember, the Word of God is a statement of the Father's will for all mankind. 

Jesus is the person called the Messiah by the Jewish people from before His crucifixion, after it, always, and forever. As the Messiah, He is the highest priest. As the highest priest, He fulfilled the Word of God by the testimony of the Father.

Jesus, God inside the flesh.

In fulfilling the Jewish prophesies of the Old Testament, Jesus gave His body to be killed. In the process, He shed His blood before and from the cross to which He was nailed in hands and feet. His body died on the cross for the atonement of sin for everyone, not just the Jews.

When Jesus was raised from the dead, alive by the Holy Ghost (the Spirit of Truth), His life before and after His death proved the Word is true; the Word never dies or changes, and the Word truly is God. Now ask yourself, "What person in their right mind would ever change the Word of God to remove the references to the spirit of the Father Himself (the Spirit of Truth aka the Holy Ghost)?" 

Comment: Please understand that, as a man, the enemy tempted Jesus to sin because Jesus had flesh, but Jesus did not sin. In other words, Jesus was capable of sin as a human because He had human flesh (and a will of the flesh), but He did not sin because He is the Word of God and believed in who He is. 

• For we have not an high priest which cannot be touched with the feeling of our infirmities; but was in all points tempted like as we are, yet without sin. Hebrew 4:15.

We must believe the Word to live forever. Remember, when we believe in Jesus and His Word, we get the power to become sons of God from Him, the only begotten son of God according to the Father's will. Only Jesus can make that claim everywhere. He proved it with His life, death, and life again.

• For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord. Romans 6:23.
• For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death. Romans 8:2.