Why does Jesus speak of himself in the third person?

One can only speculate about this, but in the synoptic gospels Jesus most likely referred to himself as 'son of man' knowing that men who would come after him would make a god out of him, and this reference would have been used to remind people that he was merely human and not the god that they would make him.

The gospel of John on the other hand, which almost didn't make it into the canon, puts the title of Jesus as 'THE Son of God' and 'Jesus Christ'. This marks the beginning of the church transforming the image of Yeshua the man into Jesus Christ the only begotten son of God -- a god and a part of the so-called 'godhead'. The gospel of John is so mixed with Greek philosophy and mythology, there is very little that could actually be referred to as gospel in the Jewish believer's sense in the early first century.

Here's my take: Jesus has different reasons in different circumstances to use this reference. Sometimes to keep "a secret", delay an event, or to allude to Daniel. Here's my example:

In all three Gospels he takes his disciples aside to predict his death. He speaks in third person. (Mt 20:17, Mark 10:32, Luke 18:31). But just a few chapters earlier he says the same thing to Peter (Mt 16:21) and the writer states that Jesus said "he" was going to be killed. In Mt 16, Peter fully understands since he tries to deter Jesus. This contrasts to Luke 18:31-34 where the disciples (Peter included) "understood none of these things". So - why be direct, then later use third person?

I think Jesus is nearing Jerusalem, and it's getting difficult. So - in this instance - he uses third person to avoid being deterred and discouraged (as Peter did earlier), and to avoid discouraging his disciples. But he alludes to the event using third person in order that - later - the disciples will remember and understand Jesus knew what he was doing and intentionally went to the cross.

To add just one more thought to the answers already posted. Jesus didn’t seem to be about the business of glorifying himself. Not only in the verses quoted here, but throughout the New Testament, when Jesus spoke about himself it appears that he was deliberately taking the focus away from himself and directing the listener’s attention back toward God, the Father.

The original questioner credited an Old Testament source, Daniel 7:13-14, as being significant in the use of the title "Son of Man". Clicking on the link takes one to the passage in the NIV, where there's also a footnote about the translation. The footnote reads:

Daniel 7:13 The Aramaic phrase bar enash means human being. The phrase son of man is retained here because of its use in the New Testament as a title of Jesus, probably based largely on this verse.

This is entirely circular. It seems to say that an incorrect translation here is likely the source of New Testament usage of "the Son of Man" as a title of Jesus. It also says that it's because of the incorrect New Testament usage that the translators of the NIV have retained "a son of man" in Daniel 7:13. It states that the correct rendering should just be: "human being".

The Biblegateway.com website allows you to display other translations side-by-side. The King James translations used the definite article and capital letters: "the Son of Man", which fits its usage as a title given to Jesus. The NIV translation retains a nod to the previous interpretation, but it's clear that the translators disagree with the interpretation given in the King James versions, by the use of the indefinite article "a" instead of "the", the removal of the capital letters, and with that footnote.

The Wikipedia article on Son of man indicates that in the Hebrew texts, when referring to the singular (son of man), the source is "ben-'adam" (literally, "son of adam"). The source in Daniel is the Aramaic "bar enash", not "ben-'adam", which the editors of the NIV have indicated should be rendered as "human being" and not "son of man", and definitely not "the Son of Man". Moreover, the use of the definite article in "the Son of Man" is said to be entirely new to the Greek texts and did not occur in the Old Testament at all.

Also, this source at The Jewish Encyclopaedia, while favoring the interpretation of Daniel 7:13 as a reference to the Messiah, claims that "son of man" is an often used expression of the time, used to refer to oneself. It has no divine connotations in such usage.

I've had a book I'd been meaning to read called Misquoting Jesus: The story behind who changed the Bible and why, by Bart D. Ehrman. One point from the back cover reads "The King James Bible was based on inferior manuscripts that in many cases do not accurately represent the meaning of the original text."

I think a large part of His reason for doing this is to make shed more light on His identity. The title used reflects additional information about the person using it. So, to look at a few of Jesus's many titles:

• "son of man" -> associates Jesus with the glorious figure seen in Daniel 7
• "son of David" -> associates Jesus with the promise God made to David about a descendant who would sit on the throne forever
• "son of God" -> describes Jesus as a king (since some of the kings of Israel were called "sons of God") although it is sometimes used in other ways by other people ("Son of the living God", "the Son of God") to refer to Jesus's divine nature.
• "messiah" / "Christ" -> associates Jesus with prophecies about a prophet from God who would rescue Israel

So when Jesus used a particular title, it would evoke a particular image and bring to mind different ideas, even though they were all correct.

Short example of how this makes a difference. Say I'm trying to get into a fancy restaurant and the guy at the front is looking doubtful that I "fit in". I could say (assuming it was true):

• I'm Richard, let me in.
• I'm the son of the owner of this restaurant, let me in.
• I'm cousin to the President, let me in.

They might all be true, but I'd be gaining something from the use of different titles.

Likewise, Jesus used different titles to show different aspects of Himself. Here is a great article on some of them (although it does miss a bit theologically).