法華義疏 4.238

4.238

佛未出世有轉輪王，將兵眾欲從此道過，而兵眾即住不行，空中云「此是古佛說法處，王須避之」，故知處定。

Before the Buddha appeared in the world, there was a wheel-turning king who led his troops intending to pass through this path, but the troops immediately halted and would not advance. A voice in the sky said: "This is the place where ancient Buddhas preached the Dharma; the king must avoid it." Hence we know the place is fixed.