What is the authenticity of the حديث (Hadith) that mentions that the reciter of the Qur’an who pronounces it correctly (يُعْرِبهُ) receives ten good deeds for every letter, and the reciter who makes errors in it (يَلْحَنُ فيه) receives one good deed for every letter, and what is meant by إعراب (i'rāb - correct pronunciation/grammatical inflection) and لحن (laḥn - error/mistake) in this context?

The hadith with the aforementioned wording: "Whoever recites the Qur'an and does not vocalize it correctly (i'rab), an angel will be assigned to him to write it for him as it was revealed, with ten good deeds for each letter... And whoever recites it and vocalizes all of it correctly, four angels will be assigned to him to write for him, with seventy good deeds for each letter," has no basis and is fabricated (mawdu'). There is no benefit in explaining it. What is authentically reported in Sahih Muslim from 'Aisha, may Allah be pleased with her, is sufficient, for she said: The Messenger of Allah, peace and blessings be upon him, said: "The one who is proficient in the Qur'an will be with the noble and righteous scribes (angels), and the one who recites the Qur'an and stumbles over it, finding it difficult, will have two rewards."