I heard the Messenger of Allah ﷺ say, "People will surely ask you about everything, until they will say, 'Allah created everything, so who created Allah?'"Yazid said, Najabah bin Sabigh as-Sulami told me that he saw a group of riders come to Abu Hurayrah and ask him about this very matter. He exclaimed, "Allahu akbar! My dear friend never told me of anything except that I have seen it come to pass, and I have been waiting for this."Jafar said, It has reached me that the Prophet ﷺ said, "When people ask you about this, say, 'Allah existed before everything, Allah created everything, and Allah will remain after everything.'"
حدثنا كثير حدثنا جعفر حدثنا يزيد بن الأصم
سمعت رسول الله ﷺ يقول ليسألنكم الناس عن كل شيء حتى يقولوا الله خلق كل شيء فمن خلقه قال يزيد فحدثني نجبة بن صبيغ السلمي أنه رأى ركبا أتوا أبا هريرة فسألوه عن ذلك فقال الله أكبر ما حدثني خليلي بشيء إلا وقد رأيته وأنا أنتظره قال جعفر بلغني أن النبي ﷺ قال إذا سألكم الناس عن هذا فقولوا الله كان قبل كل شيء والله خلق كل شيء والله كائن بعد كل شيء
Its isnad is sahih. As for Najabah bin Subay, I do not know him, but his obscurity does not harm the narration since he is not part of the actual chain of transmission, and Yazid narrates it from Abu Hurairah. However, he uses it to point out a defect in the second hadith, "If people ask you," which has passed at 9004 and 9531.