For heaven’s sake beware, lest in the hope of maintaining peace now, we lose the chance of a lasting peace hereafter.

[Cavete, per deos immortales! patres conscripti, ne spe praesentis pacis perpetuam pacem amittatis.]

Marcus Tullius Cicero (106-43 BC) Roman orator, statesman, philosopher
Philippics [Philippicae; Antonian Orations], No. 7, ch. 8 / sec. 25 (7.8/7/25) (43-01 BC) [ed. Harbottle (1906)]
    (Source)

Urging the Senate to discontinue negotiations with Mark Antony.

(Source (Latin)). Other translations:

Beware, I entreat you by the immortal gods, O conscript fathers, that out of hope of present peace you do not lose perpetual peace.
[tr. Yonge (1903)]

Take care in Heaven's name, Conscript Fathers, that you do not, in the hope of present peace, lose the peace that will endure.
[tr. Ker (Loeb) (1926)]

By the Immortal Gods!, Members of the Senate, beware of losing a lasting peace in the hope of immediate peace.
[tr. Manuwald (2007)]