On one occasion Ven. Sariputta and Ven. Maha Kotthita were staying near Varanasi in the Game Refuge at Isipatana. Then in the evening, Ven. Maha Kotthita emerged from his seclusion and went to Ven. Sariputta and exchanged courteous greetings with him. After an exchange of friendly greetings & courtesies, he sat to one side. As he was sitting there, he said to Ven. Sariputta, "Now then, friend Sariputta, does the Tathagata exist after death?"
"That, friend, has not been declared by the Blessed One: 'The Tathagata exists after death.'"
"Well then, friend Sariputta, does the Tathagata not exist after death?"
"Friend, that too has not been declared by the Blessed One: 'The Tathagata does not exist after death.'"
"Then does the Tathagata both exist and not exist after death?"
"That has not been declared by the Blessed One: 'The Tathagata both exists and does not exist after death.'"
"Well then, does the Tathagata neither exist nor not exist after death?"
"That too has not been declared by the Blessed One: 'The Tathagata neither exists nor does not exist after death.'"
"Now, friend Sariputta, when asked if the Tathagata exists after death, you say, 'That has not been declared by the Blessed One: "The Tathagata exists after death."' When asked if the Tathagata does not exist after death... both exists and does not exist after death... neither exists nor does not exist after death, you say, 'That too has not been declared by the Blessed One: "The Tathagata neither exists nor does not exist after death."' Now, what is the cause, what is the reason, why that has not been declared by the Blessed One?"
"'The Tathagata exists after death' is immersed in form. 'The Tathagata does not exist after death' is immersed in form. 'The Tathagata both exists and does not exist after death' is immersed in form. 'The Tathagata neither exists nor does not exist after death' is immersed in form.
"'The Tathagata exists after death' is immersed in feeling...
"'The Tathagata exists after death' is immersed in perception...
"'The Tathagata exists after death' is immersed in fabrication...
"'The Tathagata exists after death' is immersed in consciousness. 'The Tathagata does not exist after death' is immersed in consciousness. 'The Tathagata both exists and does not exist after death' is immersed in consciousness. 'The Tathagata neither exists nor does not exist after death' is immersed in consciousness.
"This is the cause, this is the reason, why that has not been declared by the Blessed One."
See also: other suttas in the Avyakata Samyutta (and the translator's Introduction ); AN 4.42 .