Talha bin Ubaydullah reported,

Umar saw him looking dejected and said, "What is the matter with you, Abu Muhammad? You seem downcast. Perhaps the leadership of your cousin, meaning Abu Bakr, has displeased you?"Talha replied, "No," and he praised Abu Bakr . "But I heard the Prophet ﷺ say, 'There is a word which, if any servant says it at the time of his death, Allah relieves his distress and his face brightens.' Nothing prevented me from asking him about it except that I thought I would have the chance later, until he died."Umar said to him, "I know what it is."Talha asked him, "What is it?"Umar replied, "Do you know of any word greater than the word the Prophet urged upon his uncle, 'There is no god but Allah'?"Talha said, "By Allah, that is it. That is it."

حدثنا إبراهيم بن مهدي حدثنا صالح بن عمر عن مطرف عن الشعبي

عن يحيى بن طلحة بن عبيد الله عن أبيه

أن عمر رضي الله عنه رآه كئيبا فقال ما لك يا أبا محمد كئيبا لعله ساءتك إمرة ابن عمك يعني أبا بكر قال لا وأثنى على أبي بكر رضي الله عنه ولكني سمعت النبي ﷺ يقول كلمة لا يقولها عبد عند موته إلا فرج الله عنه كربته وأشرق لونه فما منعني أن أسأله عنها إلا القدرة عليها حتى مات فقال له عمر رضي الله عنه إني لأعلمها فقال له طلحة وما هي فقال له عمر رضي الله عنه هل تعلم كلمة هي أعظم من كلمة أمر بها عمه لا إله إلا الله فقال طلحة هي والله هي