Sahih Muslim Book 25, Hadith 31
When Allah's Messenger (ﷺ) was about to leave this world, there were persons (around him) in his house, 'Umar b. al-Kbattab being one of them. Allah's Apostle (ﷺ) said: Come, I may write for you a document; you would not go astray after that. Thereupon Umar said: Verily Allah's Messenger (ﷺ) is deeply afflicted with pain. You have the Qur'an with you. The Book of Allah is sufficient for us. Those who were present in the house differed. Some of them said: Bring him (the writing material) so that Allah's Messenger (ﷺ) may write a document for you and you would never go astray after him And some among them said what 'Umar had (already) said. When they indulged in nonsense and began to dispute in the presence of Allah's Messenger (ﷺ), he said: Get up (and go away) 'Ubaidullah said: Ibn Abbas used to say: There was a heavy loss, indeed a heavy loss, that, due to their dispute and noise. Allah's Messenger (ﷺ) could not write (or dictate) the document for them.
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.
Fulfil it on her behalf.