The Book of Wills
Ṣaḥīḥ Muslim 4233
ائْتُونِي بِالْكَتِفِ وَالدَّوَاةِ - أَوِ اللَّوْحِ وَالدَّوَاةِ - أَكْتُبْ لَكُمْ كِتَابًا لَنْ تَضِلُّوا بَعْدَهُ أَبَدًا
āʾtūnī bi-l-katifi wa-ad-dawāhi-awi al-lawḥi wa-ad-dawāhi-aktub lakum kitāban lan taḍillūā baʿdah abadan
Transliteration generated from the Arabic vowel marks
The full narration
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
Source
Ṣaḥīḥ Muslim · 4233