The Messenger of Allah ﷺ said, "Whoever deliberately lies about me, let him take his seat in the Fire."
حدثنا سويد بن سعيد حدثنا علي بن مسهر عن مطرف عن عطية
قال رسول الله ﷺ من كذب علي متعمدا فليتبوأ مقعده من النار
[Sahih] Ahmad narrated it in 39/3 from the hadith of Atiya bin Saad Awfi through this route. He is a tabi, well known, weak in memory, notorious for blatant concealment in transmission, see Tabaqat Mudallisin, fourth category. See also no. 1129. The hadith is mutawatir, as mentioned before, no.