Either the Holy Quran or al-Lowh al-Mahfoodh (the preserved Tablet) is being referred to, both are classical interpretations.
لا يَمَسُّهُ إِلا الْمُطَهَّرُونَ
None shall touch it, except the purified. (Surah al-Waqi’ah, 79).
There is a difference of opinion regarding the interpretation of this verse, with many scholars saying it refers to the angels touching al-Lowh al-Mahfoodh (the preserved Tablet). Other scholars felt it refers to people not being allowed to touch the Holy Quran unless they are in a state of purity. The Hanafi scholars inclined towards this interpretation.
Imam al-Wahidi narrates this interpretation for the Ayah in his Tafseer and also mentions several scholars who seemed to share this interpretation.
وقالوا: لا يجوز للمحدث، والحائض، والجنب مس المصحف. وهذا قول محمد بن علي، وعطاء، وطاوس، وسالم، والقاسم، ومذهب مالك، والشافعي. (الوسيط في تفسير القرآن المجيد)
They said it is not permitted for a person in minor ritual impurity (Hadath), a menstruating woman or a person in major ritual impurity (Janabah) to touch a copy of the Quran (Mushaf). This is the opinion of Muhamad bin Ali, Atta, Taawoos, Salim and Qasim. And it is the Madhab of Malik and Shafi. (al-Waseet, Abu al-Hasan al-Wahidi).
وقال عطاء لا يَمَسُّهُ إِلَّا الْمُطَهَّرُونَ قال: لا يقلب الورق من المصحف إلّا المتوضئ.
And Ataa said ‘None shall touch it, except the purified.’ (Means) only a person in Wudu can turn a page of the Mushaf (copy of Quran). (Tafseer al-Thalabi).
This interpretation is supported by numerous Hadith, amongst them is the following narration, which was deemed Sahih by Imam al-Dhahabi.
عَنْ حَكِيمِ بْنِ حِزَامٍ، أَنَّ النَّبِيَّ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ لَمَّا بَعَثَهُ وَالِيًا إِلَى الْيَمَنِ قَالَ: «لَا تَمَسَّ الْقُرْآنَ إِلَّا وَأَنْتَ طَاهِرٌ» هَذَا حَدِيثٌ صَحِيحُ الْإِسْنَادِ، وَلَمْ يُخَرِّجَاهُ ” التعليق – من تلخيص الذهبي: صحيح
It is narrated from Hakim bin Hizam that when the Prophet ﷺ sent him as a representative to Yemen he said, ‘Do not touch the Quran unless you are in a state of purity.’ (al-Mustadrak, 6051). (Imam Hakim said) this Hadith has a Sahih chain, but they (Bukhari and Muslim) did not narrate it. Imam al-Dhahabi (also) said the Hadith is Sahih.
And Allah (Most High) Knows Best.
– Answered by Shaykh Noorud-deen (17.06.2021)
How to respect difference of opinion?
Hadith prohibiting touching the Holy Quran without Wudu
See also (video):