增壹阿含經 17.1.p2

17.1.p2

Thus have I heard. At one time the Buddha was in Śrāvastī, at the Jeta Grove, at Anāthapiṇḍada’s park. At that time, the Bhagavān put on his robe, picked up his bowl, and departed with Rāhula to enter the city walls of Śrāvastī. Then the Bhagavān turned to his right and said to Rāhula, “You should now contemplate the impermanence of form.” Facing him, Rāhula replied, “Thusly, Bhagavān, form is impermanent.” The Bhagavān told Rāhula, “Sensation, conception, formation, and discrimination are all impermanent.” Facing him, Rāhula replied, “Thusly, Bhagavān, sensation, conception, synthesis, and discrimination are all impermanent.”