The coming of the Messiah is a fundamental part of Judaism. But is it even mentioned in the Pentateuch? I've never studied any Perashah that talks about this. And if it isn't, why is it so important?
.... The Torah testified to his coming, as Deuteronomy 30:3-5 states:
God will bring back your captivity and have mercy upon you. He will again gather you from among the nations... Even if your Diaspora is at the ends of the heavens, God will gather you up from there... and bring you to the land....
Reference to Mashiach is also made in the portion of Bilaam who prophesies about two anointed kings: the first anointed king, David, who saved Israel from her oppressors; and the final anointed king who will arise from his descendants and save Israel in the end of days. That passage Numbers 24:17-18 relates...
Similarly, with regard to the cities of refuge, Deuteronomy 19:8-9 states: 'When God will expand your borders... you must add three more cities.' This command was never fulfilled. Surely, God did not give this command in vain.
There is no need to cite proofs from the works of the prophets for all their books are filled with mention of this matter.
Two references that come to mind are Bereshis 49:10 (This comes in the section in which Jacob is giving out the blessings to his sons near his death. In the blessing to Judah he says "The scepter shall not depart from Judah, nor the student of the law from between his feet, until Shiloh comes, and to him will be a gathering of peoples.")
and Bamidbar 24:17. (This is the section where Bilaam is giving blessings after Balak hired him to curse the Jewish people. The final "blessing" is given without being prompted, and in it he states this line "I see it, but not now; I behold it, but not soon. A star has gone forth from Jacob, and a staff will arise from Israel which will crush the princes of Moab and uproot all the sons of Seth.")
These might not be completely fool-proof since they are somewhat open for translation, but these are understood to be referring to Moshiach. There is also the end of the curses which speaks of Hashem returning the blessings.
Now, although it is indeed considered a fundamental belief in Judaism it is different from other fundamental beliefs. At first glance it shouldn't have made it onto the list of principles in the first place. Understanding the nature of how to perceive God is a principle because it defines our whole perspective and relationship with God. Also, erring about the nature of God is itself close to idolatry. But why would awareness of a Moshiach make a difference?
The Abrabanel, in his Rosh Amanna ch.14 discusses this and gives three reasons for its inclusion in the list of principles of faith.
As part of the reward and punishment system it is indeed a basic and necessary foundation of Jewish belief.
So much has been spoken of why bad things happen to good people and that triggers the attitude that God doesn't pay attention to the actions of this world. The concept of a rectified era of Moshiach fixes this issue.
Just the fact that the prophets have spoken so much about it makes belief in it necessary.
Therefore, it is understandable that the Torah did not emphasize it since it is not inherently a foundation of Judaism, although it is indeed important to know and believe in it.
The Messiah is not mentioned at all. The Messianic concept is also not mentioned at all. It's hard to find sources for a non-existence in something. It's like asking if there are any radioactive ninja turtles in your lemonade, what answer can you give other than "No." ? Anyways, if you read the Torah from beginning to end you will not find anything Messianic.
Lots of people will point out that you could interpret some things to be hints for the Messiah or the Messianic age, but it's not something inherent to the plain meaning of the text.
Yes. The introduction of the concept is brought in VaYikra 4:3. It is first introduced in the context of representing the entire Jewish people and helping to re-establish their connection with HaShem.