What is the grade of the Hadith: "For the Kaaba to be demolished stone by stone is lesser in the sight of Allah than for the blood of a Muslim person to be shed"? And what is the ruling on one who errs in narrating Hadith out of forgetfulness, and is their action considered intentional lying about the Prophet, peace and blessings be upon him?

The Hadith: "To demolish the Kaaba stone by stone is easier than killing a Muslim" has not been found with this exact wording, but its meaning has been conveyed in authentic narrations. Al-Tabarani reported from Anas, elevated to the Prophet: "Whoever harms a Muslim without right, it is as if he has demolished the House of Allah." It is also authentically reported from the Prophet, peace be upon him, that he looked at the Kaaba and said: "Allah has honored you, glorified you, and magnified you, and the believer is of greater sanctity than you." It is reported by Ibn Majah that the Prophet, peace be upon him, said: "The perishing of the world is easier to Allah than the killing of a believer without right." Al-Albani authenticated the Hadith of Ibn Umar: "By the One in Whose Hand is Muhammad's soul, the sanctity of a believer is greater to Allah than your sanctity, his wealth and his blood," and the Hadith of Ibn Abbas: "And the believer is of greater sanctity to Allah than you." As for an unintentional error in narrating a Hadith, it is not considered intentional lying that warrants the threat of hellfire.