From Sahih Muslim (Hadith 4233):
Sa'id b. Jubair reported from Ibn Abbas that he said:Thursday, and what about Thursday? Then tears began to flow until I saw them on his cheeks as it they were the strings of pearls. He (the narrator) said that Allah's Messenger (ﷺ) said: Bring me a shoulder blade and ink-pot (or tablet and inkpot), so that I write for you a document (by following which) you would never go astray. They said: Allah's Messenger (may peace upon him) is in the state of unconsciousness
Reference: Muslim 4233