The Long Āgama Sūtra 7.66

7.66

「婆羅門！汝亦如是無有方便，皮剝死人而求識神，汝不可以目前現事觀於眾生。婆羅門！有比丘初夜後夜捐除睡眠，精勤不懈，專念道品，以三昧力，修淨天眼，以天眼力，觀於眾生，死此生彼，從彼生此，壽命長短，顏色好醜，隨行受報，善惡之趣，皆悉知見；汝不可以穢濁肉眼，不能徹見眾生所趣，便言無也。婆羅門！以此可知，必有他世。」

“Priest, you likewise didn’t use the right method when you peeled the skin off the dead man looking for his spirit. It’s not something that can be seen directly with your eyes when you examine sentient beings.

“Priest, suppose there’s a monk who doesn’t become sleepy from the start to the end of the night. He’s diligent and not negligent, focusing on the factors of the path. He cultivates the pure heavenly eye with the power of samādhi, and he watches sentient beings with the power of the heavenly eye. They die here and are born there, and they’re born here from there. Their life spans are long and short, and their appearances are beautiful and ugly. According to the results of their actions, they have good and bad destinations. He fully knows and sees this. You cannot witness the good and bad destinies of sentient beings with the polluted flesh eye, so you say they don’t exist. Priest, we know in this way there’s surely another world.”