I bear witness by Allah, I heard the Messenger of Allah ﷺ say, "A man from Quraysh will violate its sanctity and bring about its violation. If his sins were weighed against the sins of mankind and jinn combined, his alone would outweigh them."
حدثنا أبو النضر حدثني إسحاق بن سعيد حدثنا سعيد بن عمرو
أشهد بالله لسمعت رسول الله ﷺ يقول يحلها ويحل به رجل من قريش لو وزنت ذنوبه بذنوب الثقلين لوزنتها
Its isnad is sahih. Ishaq bin Saeed bin Amr bin Saeed, his reliability was already established at 5680. His father, Saeed bin Amr bin Saeed bin As, his reliability was already established at 5017. The hadith is found in Majma al-Zawaid 3:284, where it says, Ahmad narrated it, and its men are the men of the sahih. Something similar in meaning has already passed in the hadith of Abdullah bin Umar bin Khattab at 6200, and we pointed to this and to 7043 there.