The Bible says that Jesus was 30 years old when He went to the river Jordan to see John the Baptist and be baptized by him. (See Luke 3:23) Jesus became the "Messiah", the "Most Holy" when He was anointed by the Holy Spirit at His baptism (Acts 10:37, 38).
It is very interesting to note that Jesus, Himself, preached the Gospel. Note that Jesus says, "...The time is fulfilled, and the kingdom of God is at hand: repent ye, and believe the gospel." Mark 1:15 What did He mean, "The time is fulfilled"?
Daniel (see the Daniel 8 & 9 Timeline)
9:24 Seventy weeks are determined upon thy people and upon thy holy city, to finish the transgression, and to make an end of sins, and to make reconciliation for iniquity, and to bring in everlasting righteousness, and to seal up the vision and prophecy, and to anoint the most Holy.
(This verse tells us exactly when the "most Holy" would be anointed as the "Messiah". Jesus was anointed as the Messiah right on time.)
Luke
3:21 Now when all the people were baptized, it came to pass, that Jesus also being baptized, and praying, the heaven was opened,
3:22 And the Holy Ghost descended in a bodily shape like a dove upon him, and a voice came from heaven, which said, Thou art my beloved Son; in thee I am well pleased.
Mark
1:9 And it came to pass in those days, that Jesus came from Nazareth of Galilee, and was baptized of John in Jordan.
1:10 And straightway coming up out of the water, he saw the heavens opened, and the Spirit like a dove descending upon him:
1:11 And there came a voice from heaven, [saying], Thou art my beloved Son, in whom I am well pleased.
1:12 And immediately the Spirit driveth him into the wilderness.
1:13 And he was there in the wilderness forty days, tempted of Satan; and was with the wild beasts; and the angels ministered unto him.
Matthew
3:13 Then cometh Jesus from Galilee to Jordan unto John, to be baptized of him.
3:14 But John forbad him, saying, I have need to be baptized of thee, and comest thou to me?
3:15 And Jesus answering said unto him, Suffer [it to be so] now: for thus it becometh us to fulfil all righteousness. Then he suffered him.
3:16 And Jesus, when he was baptized, went up straightway out of the water: and, lo, the heavens were opened unto him, and he saw the Spirit of God descending like a dove, and lighting upon him:
3:17 And lo a voice from heaven, saying, This is my beloved Son, in whom I am well pleased.
4:1 Then was Jesus led up of the Spirit into the wilderness to be tempted of the devil.
4:2 And when he had fasted forty days and forty nights, he was afterward an hungered.
4:3 And when the tempter came to him, he said, If thou be the Son of God, command that these stones be made bread.
4:4 But he answered and said, It is written, Man shall not live by bread alone, but by every word that proceedeth out of the mouth of God.
4:5 Then the devil taketh him up into the holy city, and setteth him on a pinnacle of the temple,
4:6 And saith unto him, If thou be the Son of God, cast thyself down: for it is written, He shall give his angels charge concerning thee: and in [their] hands they shall bear thee up, lest at any time thou dash thy foot against a stone.
4:7 Jesus said unto him, It is written again, Thou shalt not tempt the Lord thy God.
4:8 Again, the devil taketh him up into an exceeding high mountain, and showeth him all the kingdoms of the world, and the glory of them;
4:9 And saith unto him, All these things will I give thee, if thou wilt fall down and worship me.
4:10 Then saith Jesus unto him, Get thee hence, Satan: for it is written, Thou shalt worship the Lord thy God, and him only shalt thou serve.
4:11 Then the devil leaveth him, and, behold, angels came and ministered unto him.
For further study, read: