I have read it somewhere and can't remember now. Buddha told Bhikkus that he never admires a disiple who stops his effort after attaining "sotapanna" state. He should still work hard until he is completely clean and attains Arhat status.
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1There are suttas where the Buddha "spits" on birth AND death and there is a Sutta where the sublime Buddha explained Ven. Ananda, why he did not taught much about the blessing of sotapanna (so that they would strive further. A combination... my person doubts. – Samana Johann Jan 20 '18 at 11:15
The thing you are looking for is probably a misinterpretation of this passage from Maha-Parinibbana Sutta:
... among these five hundred bhikkhus even the lowest is a stream-enterer, secure from downfall, assured, and bound for enlightenment."
- And the Blessed One addressed the bhikkhus, saying: "Behold now, bhikkhus, I exhort you: All compounded things are subject to vanish. Strive with heedfulness!"
Handa dani bhikkhave amantayami vo: Vayadhamma sankhara appamadena sampadetha.
And this one in regards to Samsara:
“Just as even a little dung stinks, so I do not recommend even a little becoming, not for so much as a finger snap”
