Sahih Bukhari
Prophetic Commentary on the Quran (Tafseer of the Prophet (PBUH))
Volume: 006 / Book Number: 060 / Hadith Number: 221
Narrated Al-Bara bin Azib:
Allah's Apostle said, "When a Muslim is questioned in his grave, he will testify that none has the right to be worshipped but Allah and that Muhammad is Allah's Apostle, and that is what is meant by Allah's Statement:--
"Allah will keep firm those who believe with a Word that stands firm in this world and in the Hereafter." (14.27)