This was said by the Buddha, the Perfected One: that is what I heard.
Vuttañhetaṁ bhagavatā vuttamarahatāti me sutaṁ:
“Mendicants, give up one thing
“Ekadhammaṁ, bhikkhave, pajahatha;
and I guarantee you non-return.
ahaṁ vo pāṭibhogo anāgāmitāya.
What one thing?
Katamaṁ ekadhammaṁ?
Conceit is the one thing. Give it up,
Mānaṁ, bhikkhave, ekadhammaṁ pajahatha;
and I guarantee you non-return.”
ahaṁ vo pāṭibhogo anāgāmitāyā”ti.
The Buddha spoke this matter.
Etamatthaṁ bhagavā avoca.
On this it is said:
Tatthetaṁ iti vuccati:
“Drunk on conceit,
“Yena mānena mattāse,
beings go to a bad place.
sattā gacchanti duggatiṁ;
Having rightly understood that conceit,
Taṁ mānaṁ sammadaññāya,
the discerning give it up.
pajahanti vipassino;
Once they’ve given it up,
Pahāya na punāyanti,
they never return to this world.”
imaṁ lokaṁ kudācanan”ti.
This too is a matter that was spoken by the Blessed One: that is what I heard.
Ayampi attho vutto bhagavatā, iti me sutanti.
My interpretation is that aim for the stars, can fall on the moon.
Conceit is only totally removed at arahanthood, but possibly by just tackling head on, one can go quite far until non-returner, but not completely removed it yet.
I just want to add something for the sake of clarity regarding my thinking above(personal opinion). For example, lobha is not only abandoned at the fourth stage of enlightenment. By far the biggest abandonment happens at the first stage of enlightenment. A great flood trickles down to a stream that can only sweep along for a maximum of eight lives. In this sense it could also have been said, give up this one thing ‘lobha’ for the guarantee of stream entry.