What is the Hadith that refers to the the verses of protection (Ayat al-Hirs) that Imam Ibn Qudamah used to recite after the Fajr prayer? How authentic is this Hadith, and does it fall under the permissibility of acting upon a weak Hadith, which is agreed upon among scholars?

We have not come across hadiths related to the verses of protection (ayat al-hiras). Al-Suyuti mentioned that much of what is narrated about the special properties of the Qur'an has no basis other than the experiences of some pious individuals. Abu Shamah stated that collecting specific verses and naming them "verses of protection" has no origin. However, some contemporary scholars followed Abu Shamah, while it was narrated that Ibn Qudamah, Ibn Rajab, Al-Dhahabi, and Ibn Muflih did so, which indicates that declaring this an innovation is not a matter of consensus. We would like to point out that the questioner's statement that there is a scholarly consensus on the desirability of acting upon a weak hadith is not absolute, as there is disagreement on this issue.