Imam Ahmad recorded that Asma' bint Yazid bin As-Sakan said, "I heard the Messenger of Allah say about these two Ayat,
﴿ ٱللَّهُ لَآ إِلَـٰهَ إِلَّا هُوَ ٱلۡحَىُّ ٱلۡقَيُّومُۚ ﴾
(Allah! None has the right to be worshipped but He, the Ever Living, the One Who sustains and protects all that exists) (2:255), and,
﴿ الٓمٓ • ذَٲلِكَ ٱلۡڪِتَـٰبُ لَا رَيۡبَۛ فِيهِۛ هُدً۬ى لِّلۡمُتَّقِينَ ﴾
(Alif-Lam-Mim. Allah! None has the right to be worshipped but He, the Ever Living, the One Who sustains and protects all that exists) (3:1-2),
« إِنَّ فِيهِمَا اسْمَ اللهِ الْأَعْظَم »
(They contain Allah's Greatest Name.)
This is also the narration collected by Abu Dawud, At-Tirmidhi and Ibn Majah, and At-Tirmidhi said, "Hasan Sahih''.
Further, Ibn Marduwyah recorded that Abu Umamah reported that the Prophet said,
« اسْمُ اللهِ الْأَعْظَمُ، الَّذِي إِذَا دُعِيَ بِهِ أَجَابَ، فِي ثَلَاثٍ: سُورَةِ الْبَقَرَةِ وَآلِ عِمْرَانَ وَطه »
(Allah's Greatest Name, if He was supplicated with it, He answers the supplication, is in three Surahs - Al-Baqarah, Al `Imran and Ta-Ha.)
Hisham bin `Ammar, the Khatib (orator) of Damascus (one of the narrators in the above narration), said, "As for Al-Baqarah, it is in,
﴿ ٱللَّهُ لَآ إِلَـٰهَ إِلَّا هُوَ ٱلۡحَىُّ ٱلۡقَيُّومُۚ ﴾
(Allah! None has the right to be worshipped but He, the Ever Living, the One Who sustains and protects all that exists) ﴿2:255﴾; in Al `Imran, it is in,
﴿ الٓمٓ • ذَٲلِكَ ٱلۡڪِتَـٰبُ لَا رَيۡبَۛ فِيهِۛ هُدً۬ى لِّلۡمُتَّقِينَ ﴾
(Alif-Lam-Mim. Allah! None has the right to be worshipped but He, the Ever Living, the One Who sustains and protects all that exists) (3:1-2), while in Ta-Ha, it is in,
﴿ وَعَنَتِ ٱلۡوُجُوهُ لِلۡحَىِّ ٱلۡقَيُّومِۖ ﴾
(And (all) faces shall be humbled before (Allah), the Ever Living, the One Who sustains and protects all that exists) (20:111).''