What a contrast to this civil war in our midst! Here, set deep inside the country, are conspiracy, danger and a deadly foe. Degeneracy, madness and evil are the enemies we have to fight.

[Domesticum bellum manet, intus insidiae sunt, intus inclusum periculum est, intus est hostis. cum luxuria nobis, cum amentia, cum scelere certandum est.]

Marcus Tullius Cicero (106-43 BC) Roman orator, statesman, philosopher
Orationes in Catilinam [Catilinarian Orations], No. 2, ch. 5 / § 11 (2.5.11) (63-11-09 BC) [tr. Grant (1960)]
    (Source)

Cicero argues that, having achieved peace with other nations, the danger to Rome is now the internal one of Catiline and his decadent, wastrel followers.

(Source (Latin)). Alternate translations:

The Plot is within; the danger locked within; the Enemy is within: We have a Conflict with Luxury, with Madness, with Treachery.
[tr. Wase (1671)]

Our only danger is at home; treason lurks within our walls; the enemy is in the heart of the city. Luxury, villainy, and madness, are the foes we are to encounter.
[tr. Sydney (1795)]

Domestic war alone remains. The only plots against us are within our own walls, -- the danger is within, -- the enemy is within. We must war with luxury, with madness, with wickedness.
[tr. Yonge (1856)]

A war at home remains; the snares are within; the danger is inclosed within; the enemy is within; we have to contend with luxury, with madness, with guilt.
[tr. Mongan (1879)]

A domestic war remains; the snares are within; the danger is inclosed within; the enemy is within; it is to be contended to (by) us with luxury, with madness, with crime.
[tr. Underwood (1885)]

A domestic war remains; the ambuscades are within; the danger is enclosed within; the enemy is within; (it) is to [must] be contended by us [we must contend] with luxury, with madness, with crime.
[tr. Dewey (1916)]

The enemy is within the gates; it is with our own luxury, our own folly, our own criminality that we have to contend.
[tr. Taylor (1916)]