Assalaamu alaykum wa rahmatullaahi wa barakaatuhu. Was the Quran revealed to the Prophet, sallallaahu 'alayhi wa sallam, with the rules of Tajweed (the rules of the recitation of the Quran) already in it? For example: Ikhfaa'a (hiding) or Idghaam (merging) or Ghunna (nasalization), Qalqala, ... There are also specific letters that are elongated throughout the Quran, such as the letter Dhaaaaalin in Surah Al-Faatihah. Did the Prophet, sallallaahu 'alayhi wa sallam, recite the Quran with these rules? Did Jibreel (Gabriel), may Allaah exalt his mention, recite it to the Prophet, sallallaahu 'alayhi wa sallam, with the Tajweed which I mentioned above? I hope you understand my question. Thank you.

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger. 

The Prophet recited the Quran with the rules of Tajweed as he received it from Jibreel, may Allah exalt his mention. This Tajweed includes the pronunciation of the letters and their characteristics and all other matters that are related to the rules of Tajweed.

Ibn Al-Jazari said in his famous poem about the rules of Tajweed (what means):

Applying the Tajweed is something quite obligatory ... and whoever recites the Quran without Tajweed is sinful

Because it was revealed as such from the Lord ... and that is how from Him it reached us

The book Al-Waafi commented on the above verses of Al-Jazari's poem, saying:

"What is meant by that is that Allah revealed the Quran with Tajweed, and the Prophet received it orally like this from Jibreel, may Allah exalt his mention. Allah revealed the command to recite the Quran with Tajweed in the Quran, as Allah says (what means): {…and recite the Quran with measured recitation...} [Quran 73:4] It is known that the Prophet used to recite the Quran with Tajweed, as it was revealed to him, so though this verse addresses him, what is meant is his nation. It was reported that ‘Ali, may Allah be pleased with him, said, 'Measured recitation (Tarteel) is the Tajweed of the letters and the knowledge of pauses and stops.'"

Until he said:

"'And that is how from Him it reached us'; i.e. the Quran reached us from Allah through the trustworthy Jibreel with Tajweed to the Prophet – as we said – from the Preserved Tablet, and the Prophet conveyed it to the Companions, and then the Taabi’is (generation following that of the Companions) and their followers learned it as such (from generation to generation) to our Shaykhs – – with Tawaatur (the multiplicity of the sources of a certain report that leads to certitude in the listener that the report is indeed true) with the description of the Tarteel that includes the Tajweed and the pronunciation and articulation of the letters and their descriptions and all other related matters which are significant in the Arabic language and by which the Quran was revealed; Allah says (what means): {And We did not send any messenger except [speaking] in the language of his people…} [Quran 14:4]; so it is an obligation that all the rules of the Arabs be taken into account in regard to matters that change the structure or corrupt the meaning, and it is desirable in regard to matters that make the pronunciation more beautiful. We said that it is desirable in this kind because hidden mistakes are only known by the skilled reciters in regard to the mispronunciation of the letters r, n, and l."

For more benefit, please refer to fatwa 86574.

Allah knows best.