Sunan Ibn Majah Book 34, Hadith 30
The Greatest Name of Allah, if He is called by which He will respond, is in three Surah: Al-Baqarah, Al 'Imran and Ta-Ha. (Hasan)Another chain for something similar from Al-Qasim, from Abu Umamah, from the Prophet (saas).
the Messenger of Allah (saas) said: "The Greatest Name of Allah is in these two Verses: And your Ilah (God) is One Ilah (God - Allah), La Ilaha Illa Huwa (none has the right to be worshipped but He), the Most Gracious, the Most Merciful.' And at the beginning of Surah Al 'Imran."
"The Prophet (saas) heard a man say: 'Allahumma! Inni as'aluka bi-annaka Antallahul-Ahadus-Samad, alladhi lam yalid wa lam yuwlud, wa lam yakun lahu kufuwan ahad (O Allah! I ask You by virtue of Your being Allah, the One, the Self-Sufficient Master, Who begets not nor was begotten, and there is none co-equal or comparable to Him).' The Messenger of Allah (saas) said: 'He has asked Allah by His Greatest Name, which if He is asked thereby He gives, and if He is called upon thereby He answers.'"