In the moment of our talking, envious time has ebb’d away.
Seize the present; trust tomorrow e’en as little as you may.
 
[Dum loquimur, fugerit invida
aetas: carpe diem, quam minimum credula postero.]

Horace (65-8 BC) Roman poet and satirist [Quintus Horacius Flaccus]

Odes [Carmina], Book 1, # 11, l. 8ff (1.11.8-9) (23 BC) [tr. Conington (1872)]

Often titled "To Leuconoë." This is the source of the famous phrase, "carpe diem," commonly translated "seize the day." Many scholars give it a more horticultural spin, to harvest the day now, while it is ripe. More discussion here. More quotations along this theme here.

(Source (Latin)). Alternate translations:

Whilest we are talking, envious Time doth slide:
This day's thine own, the next may be deny'd.
[tr. Sir T. H.; ed. Brome (1666)]

Time, while we speak on't flyes; now banish sorrow,
Live well to day, and never trust to morrow.
[tr. S. W., Esq.; ed. Brome (1666)]

E'en whil'st we speak the Envious time
Doth make swift hast away,
Then seize the present, use thy prime,
Nor trust another Day.
[tr. Creech (1684)]

While we are conversing, envious age has been flying; seize the present day, not giving the least credit to the succeeding one.
[tr. Smart/Buckley (1853)]

Use all life's powers,
The envious hours
Fly as we talk ; then live to-day,
Nor fondly to to-morrow trust more than you must and may.
[tr. Martin (1864)]

While we talk, grudging Time will be gone, and a part of ourselves be no more.
Seize to-day -- for the morrow it is in which thy belief should be least.
[tr. Bulwer-Lytton (1870)]

Our span is brief. The niggard hour,
in chatting, ebbs away;
Trust nothing for to-morrow's sun:
make harvest of to-day.
[tr. Gladstone (1894)]

E'en while we speak, envious life will fly; --
So make use of to-day, trusting the next, little as possible.
[tr. Phelps (1897)]

While we are talking envious time steals on:
Catch to-day's joy and give the morrow but a minimum of trust.
[tr. Garnsey (1907)]

Ev'n as we speak, grim Time
speeds swift away;
Seize now and here the hour that is. nor trust
some later day!
[tr. Marshall (1908)]

Even while we speak, envious Time has sped. Reap the harvest of to-day, putting as little trust as may be in the morrow!
[tr. Bennett (Loeb) (1912)]

E'en while we speak time, grudging time, has fled; snatch eagerly
Each day, and trust the morrow's grace as little as may be.
[tr. Mills (1924)]

Even while
We talk Time, hateful, runs a mile.
Don't trust tomorrow's bough
For fruit. Pluck this, here, now.
[tr. Michie (1963)]

Time goes running, even
As we talk. Take the present, the future's no one's affair.
[tr. Raffel (1983)]

Now as I say these words,
Time has already fled
Backwards away --
Leuconoe --
Hold on to the day.
[tr. Ferry (1997)]

While we converse, envious time will have vanished: harvest
Today, placing the least credence on what’s to come.
[tr. Willett (1998)]

Even as we speak, envious Time is fleeing.
Seize the day: entrusting as little as possible to tomorrow.
[tr. Alexander (1999)]

The envious moment is flying now, now, while we’re speaking:
Seize the day, place in the hours that come as little faith as you can.
[tr. Kline (2015)]

While we are speaking, envious life
will have fled: seize the day, trusting the future as little as possible.
[tr. Wikisource (2021)]