Buraidah ibn husaib (RA) said: The Prophet (ﷺ) heard a man supplicating, and he was saying:
اَللَّهُمَّ إِنِّي أَسْأَلُكَ بِأَنِّي اَشْهَدُ أَنَّكَ أَنْتَ اللَّهُ لَا إِلَهَ إِلَّا أَنْتَ الْأَحَدُ الصَّمَدُ الَّذِيْ لَمْ يَلِدْ وَلَمْ يُوْلَدْ وَلَمْ يَكُنْ لَّهُ كُفُوًا أَحَدٌ
اَللّٰهُمَّ اِنِّىْ اَسْاَلُكَ بِاَنِّىْ اَشْهَدُ اَنَّكَ اَنْتَ اللّٰهُ لَا اِلٰهَ اِلَّا اَنْتَ الْاَحَدُ الصَّمَدُ الَّذِىْ لَمْ يَلِدْ وَلَمْ يُوْلَدْ وَلَمْ يَكُنْ لَّهٗ كُفُوًا اَحَدٌ
Allaahumma 'innee 'as'aluka bi'annee 'ash-hadu 'annaka 'AntAllahu laa 'ilaaha 'illaa 'Antal-'Ahadus-Samadul-ladhee lam yalid wa lam yoolad wa lam yakun lahu kufuwan 'Ahad
O Allah, I ask You, by the fact that I bear witness that You are Allah. There is none worthy of worship but You, the Only ilah, Independent of creation, Who was not begotten and begets not, and none is equal to Him.
Then the Prophet (ﷺ) said, ‘By the One in Whose Hand is my soul, he has asked Allah by His Greatest Name, the one which if He is called upon by it, He responds, and when He is asked by it, He gives.