It was narrated from Samurah bin Jundub that:
The Prophet (ﷺ) said: '"Whoever narrated a Hadith from me thinking it to be false, then he is one of the two liars." (ID)
English reference (ID): Vol. 1, Book 1, Hadith 39 (ID)
Arabic reference (ID): Book 1, Hadith 40 (ID)