Dvarim #1:

One thing that might strike you as you look over this week's parsha is that it is quite a mouthful! Moshe gave a lengthy oration, detailing recent Jewish history, giving mussar, giving blessings and encouragement, and telling them a bit about what would happen to them in later times - about four prakim worth. Most of the book of Dvarim consists of a long speech, or speeches. (Rabbi Berel Wein writes "he delivers an impassioned six month long oration which comprises most of the Book of Dvarim.") This is quite a change from his initial attitude. He originally, in Shemot 4, protested that he was not a man of words.

בִּי אֲדֹנָי, לֹא אִישׁ דְּבָרִים אָנֹכִי גַּם מִתְּמוֹל גַּם מִשִּׁלְשֹׁם, גַּם מֵאָז דַּבֶּרְךָ אֶל-עַבְדֶּךָ: כִּי כְבַד-פֶּה וּכְבַד לָשׁוֹן, אָנֹכִי
'Oh Lord, I am not a man of words, neither heretofore, nor since Thou hast spoken unto Thy servant; for I am slow of speech, and of a slow tongue.'

This could be viewed as the development of Moshe Rabbeinu in his role as leader, an idea worth developing.

However, a different perspective is given by Rabbi Tanchuma, cited in Midrash Rabba, gives an interesting analogy, to explain this. He assumes a static Moshe Rabbeinu, and explains this inconsistency of attitude as follows:

ד"א אלה הדברים אמר ר' תנחומא למה"ד לאדם שהיה מוכר ארגמן והיה מכריז הרי ארגמן הציץ המלך ושמע את קולו קרא אותו וא"ל מה אתה מוכר א"ל לא כלום א"ל אני שמעתי את קולך שהיית אומר הרי ארגמן ואתה אומר לא כלום א"ל מרי אמת ארגמן הוא אלא אצלך אינו כלום. כך משה לפני הקב"ה שברא את הפה ואת הדיבור אמר (שם ד) לא איש דברים אנכי אבל אצל ישראל כתיב בו אלה הדברים
Another explanation. "These are the words..." R' Tanchuma said, to what can this matter be compared? To a man who sold Argaman (purple), and would call out "Here is Argaman." The King peered out and heard his voice. He {King} called him and said to him, "What are you selling?" He replied, "Nothing." He {King} said to him, "I heard your voice that was saying, 'Here is Argaman' and you are saying 'Nothing!' He replied, "My master, in truth it is Argaman, but for {in quality} as regards you it is nothing. So did Moshe, before Hashem who created the mouth and speech, said "I am not a man of words," but by Israel it is written as regards him, "These are the words..."

It is interesting that the explanation in part comes from Hashem's next words, that is, Hashem's response to Moshe's claim that he is not a man of words. Hashem says:

? מִי שָׂם פֶּה לָאָדָם, אוֹ מִי-יָשׂוּם אִלֵּם, אוֹ חֵרֵשׁ אוֹ פִקֵּחַ אוֹ עִוֵּר--הֲלֹא אָנֹכִי, ה.
'Who hath made man's mouth? or who maketh a man dumb, or deaf, or seeing, or blind? is it not I the LORD?'

Of course Hashem then tells him that He will be with Moshe's mouth, and help him out in this regard, which would be another answer to how Moshe can give such a lengthy speech. However, that perhaps was only regarding addressing Pharaoh.

At any rate, I thought it was worthy to point out that R' Tanchuma takes his cue from that same response of Hashem, but on a midrashic level. This is as opposed to constructing an answer to this from thin air. I feel that this is quite often how midrashim work.

R' Tanchuma's answer was basically that compared with Hashem, the creator of speech, Moshe is not a man of words, but in addressing Israel, he can hold his own.

Another twist to this midrash, which I'm almost positive I spoke about earlier on parshablog, but could not find it, is the argaman angle. During 100 BCE to 68 CE, "Caesar and Augustus restricted the use of dyes {J: both techelet and argaman} to the governing classes. Nero issues a decree that gave the emperor exclusive right to wear purple or blue garments." During 337 CE to 383 CE, "[u]nder Constantius (337-362) the restrictions against the use of tekhelet were strictly enforced. An edict (383) by Gratian, Valentinian, and Theodosius made the manufacture of higher quality purple and blue a state monopoly." (See timeline by Naron.)

So, we can see why the seller may have been reluctant to reveal to the king that he was dealing in argaman. And perhaps we can understand his response a bit more. It is a type of purple, but not of royal quality, so please don't strike me down! It is of inferior quality, though it could be called purple.