Dear friend Hakimi sahib,
Thank you for your comment on parts of my comment. Regarding the differentiation of Dari, Farsi and Tajik languages, just in order to avoid a long talk about the origin of the Dari language, it is enough to quote here only two short quotes from the Persian researchers themselves about what Dari is, where it comes from, and what its tradition is:
Nafisi: "...Iranian literature, as far as the information is available, covers a period of nearly two thousand and six hundred years. During this period, four major languages were common in Iran and works have been left in all four languages: Avesta language [Nafisi does not want to say the language of Balkh - S, R] ancient Persian, Pahlavi, Dari language or modern Persian. The oldest language of which there are traces left is the language of Avestan, and apparently this language was used in a typical period of the Iranian race, when our ancestors had not yet come to today's Iran. There is a lot of disagreement about the area where the Iranian race lived before coming to today's Iran, and the better opinion is that they were in the north and south of the Hindu Kush Mountains, and from there they came to three different places in today's Iran. Once in three thousand and three hundred years ago and again in two thousand and seven hundred years ago and the third time in 2670 years ago. The language of our fathers, when they had not yet come to Iran, was a language that was called the Avesta language because the book of Avesta was written in it. .. »
Afghan researcher Suleiman Ravash's note about Nafisi's speech: "Nafisi, a Persian researcher and linguist, calls the Balkhi language the Avesta language. While in reality it is a Balkhi language because as it was said, the Avesta was written in Balkh and in the time of Gashtasip by the great Zoroaster. Also, Nafisi explains the migration of the Fars tribe from Balkh, which is the country of Bakhdi. He also mentions ancient Persian and Pahlavi language as the Dari language, which is known as Farsi in Iran today. Therefore, it can be said that the name of Dari precedes Persian.
Suleiman Ravash: Let me rewrite the words of Mohammad Taqi Bahar, the "King of Poetry" of Iran. {It should be noted that Bahar himself is Khorasani} I refer to the history. According to historical traditions, after Bahman, his daughter "Homai" will become the king. Until the time of Bahman, the son of Esfandiar was on the throne of Balkh country, of which Fars is a part of the provinces. As history narrates, Cyrus, whom the Persians call the Great, was one of Bahman's governors in Iraq. We read in Mourawije-ul- Zahab of Masoudi that: "... Cyrus was an Iranian who had a kingdom in Iraq on behalf of Bahman, and at that time Bahman's seat was Balkh."
"Parsig" (also known as Old Persian today) and Pahlavi, the common language of the Sasanians, was only the language of a minority in the Sasanian's Empire whose speakers lived in the provinces of Pars, but this language in the land of the Medes (Azerbaijan, Kurdistan and Tabaristan) and The lands beyond it were more common. However, at that time there were several different dialects in the land of Persia.