Jabir bin Abdullah reported,

I heard Umar bin Khattab رضي الله عنه say to Talha bin Ubaydullah, "Why is it that I see you looking dishevelled and dust-covered ever since the Messenger of Allah ﷺ passed away? Perhaps, Talha, you are troubled by your cousin holding the position of leader?"Talha replied, "Allah forbid. I am the most unlikely of you to do such a thing. But I heard the Messenger of Allah ﷺ say, 'I know of a word which no one says at the moment of death without his soul finding ease through it as it leaves his body, and it will be a light for him on the Day of Resurrection.' I did not ask the Messenger of Allah ﷺ about it, and he did not inform me of it. That is what has been weighing on me."Umar رضي الله عنه said, "I know it."Talha said, "Praise be to Allah. What is it?"Umar replied, "It is the word he spoke to his uncle, La ilaha illa Allah."Talha said, "You have spoken the truth."

Ahmad 187

Sahih

حدثنا عبد الله بن نمير عن مجالد عن عامر

عن جابر بن عبد الله قال

سمعت عمر بن الخطاب رضي الله عنه يقول لطلحة بن عبيد الله ما لي أراك قد شعثت واغبررت منذ توفي رسول الله ﷺ لعلك ساءك يا طلحة إمارة ابن عمك قال معاذ الله إني لأجدركم أن لا أفعل ذلك إني سمعت رسول الله ﷺ يقول إني لأعلم كلمة لا يقولها أحد عند حضرة الموت إلا وجد روحه لها روحا حين تخرج من جسده وكانت له نورا يوم القيامة فلم أسأل رسول الله ﷺ عنها ولم يخبرني بها فذلك الذي دخلني قال عمر رضي الله عنه فأنا أعلمها قال فلله الحمد فما هي قال هي الكلمة التي قالها لعمه لا إله إلا الله قال طلحة صدقت

أحمد 187صحيح
Contents
Reference
Commentary
Ayat
Collection
Musnad Ahmad
Book
Umar bin Khattab
Numbering
Darussalam 187
Ahmad 187