Assurance
Assāsa Sutta  (SN 38:5)

On one occasion Ven. Sāriputta was staying in Magadha near Nāla Village. Then Jambukhādaka the wanderer went to Ven. Sāriputta and, on arrival, 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. Sāriputta: “‘A person who has attained assurance, a person who has attained assurance,’ it is said, my friend Sāriputta. To what extent is one a person who has attained assurance?”

“Friend, when a monk discerns, as it has come to be, the origination, passing away, allure, drawbacks of—and escape from—the six media of (sensory) contact: It’s to this extent that he is a person who has attained assurance.”

“But is there a path, is there a practice for the realization of this assurance?”

“Yes, there is a path, there is a practice for the realization of this assurance.”

“Then what is the path, what is the practice for the realization of this assurance?”

“Precisely this noble eightfold path, my friend: right view, right resolve, right speech, right action, right livelihood, right effort, right mindfulness, right concentration. This is the path, this is the practice for the realization of this assurance.”

“It’s an auspicious path, my friend, an auspicious practice for realization of this assurance—enough for the sake of heedfulness.”

See also: SN 48:3