اَللَّهُ أَحَدٌ، اللَّهُ الصَّمَدُ، لَمْ يَلِدْ وَلَمْ يُولَدْ، وَلَمْ يَكُن لَّهُ كُفُوًا أَحَدٌ

Allahu 'Ahad. Allahus-Samad. Lam yalid wa lam yoolad. Wa lam yakun lahu kufuwan 'ahad

He is Allah, [who is] One, Allah, the Eternal Refuge. He neither begets nor is born, Nor is there to Him any equivalent. Abu Hurairah (RA) reported that Messenger of Allah (ﷺ) said: People will continue to ask one another(questions) till this is pronounced: Allah created all things, but who created Allah ? Whoever comes across anything of that, he should say: (The dua is mentioned above) Then he spit three times on his left side, seeking refuge with Allah from Satan.

Reference: Hasan. Abu Dawud: 4722