Saṃyuktāgama 172. [First Discourse on Eradicating Impermanent Things]
Thus have I heard. At one time the Buddha was staying at Sāvatthī in Jeta's Grove, Anāthapiṇḍika's Park.
At that time the Blessed One said to the monks: “You should eradicate those things that are impermanent. Having eradicated those things will be for your benefit and welfare, for your peace and happiness for a long time. What things are impermanent? Bodily form is impermanent, feeling … perception … formations … consciousness is impermanent.”
When the Buddha had spoken this discourse, hearing what the Buddha had said the monks were delighted and received it respectfully.