It was narrated that 'Abdur-Rahman bin Abi Laila said:
We said to Zaid bin Arqam: 'Tell us a Hadith from the Messenger of Allah (ﷺ).' He said: 'We have grown old and have forgotten, and (narrating) Ahadith from the Messenger of Allah (ﷺ) is difficult (not a simple matter).'" (ID)
English reference (ID): Vol. 1, Book 1, Hadith 25 (ID)
Arabic reference (ID): Book 1, Hadith 26 (ID)