The Long Āgama Sūtra 18.33

18.33

佛言：「如是答，依法順法，不違也。所以然者？過去三耶三佛與我等，未來三耶三佛與我等，欲使現在有二佛出世，無有是處。」

The Buddha said, “Such an answer would rely on and align with the Dharma; you wouldn’t contradict it. Why is that so? The complete and correct Buddhas of the past were my equals, and the complete and correct Buddhas of the future will be my equals, but it isn’t possible for there to be two Buddhas who arise in the world in the present.”