“The invocation of social necessity should alert us. It contains the seeds for Marx's critique of political economy as well as for his dissection of capitalism.”

No Compromise – No Political Trading (1899)
Context: This foundation of the class struggle, which Marx – and this is his immortal service – has given to the modern labor movement, is the main point of attack in the battle which the bourgeois political economy is waging with socialism. The political economists deny the class struggle and would make of the labor movement only a part of the bourgeois party movements, and the Social Democracy only a division of the bourgeois democracy. The bourgeois political economy and politics direct all their exertions against the class character of the modern labor movement. If it were possible to create a breach in this bulwark, in this citadel of the Social Democracy, then the Social Democracy is conquered, and the proletariat thrown back under the dominion of capitalistic society. However small such a breach may be in the beginning, the enemy has the power to widen it and the certainty of final victory. And the enemy is most dangerous when he comes as a friend to the fortress, when he slinks in under the cover of friendship, and is recognized as a friend and comrade. The enemy who comes to us with open visor we face with a smile; to set our foot upon his neck is mere play for us. The stupidly brutal acts of violence of police politicians, the outrages of anti-socialist laws, the anti-revolution laws, penitentiary bills – these only arouse feelings of pitying contempt; the enemy, however, that reaches out the hand to us for a political alliance; and intrudes himself upon us as a friend and brother, – him and him alone have we to fear. Our fortress can withstand every assault – it can not be stormed nor taken from us by siege – it can only fall when we ourselves open the doors to the enemy and take him into our ranks as a fellow comrade. Growing out of the class struggle, our party rests upon the class struggle as a condition of its existence. Through and with that struggle the party is unconquerable; without it the party is lost, for it will have lost the source of its strength. Whoever fails to understand this or thinks that the class struggle is a dead issue, or that class antagonisms are gradually being effaced, stands upon the basis of bourgeois philosophy.

Source: The Limits To Capital (2006 VERSO Edition), Chapter 2, Production and Distribution, p. 39

Source: Doing Virtuous Business (Thomas Nelson, 2011), p. 9.

These deep-rooted affinities are normally passed over in pious silence; they nevertheless constitute, from Epicurus to Spinoza and Hegel, the premises of Marx's materialism. They are hardly ever mentioned, for the simple reason that Marx himself did not mention them, and so the whole of the Marx-Hegel relationship is made to hang on the dialectic, because this Marx did talk about!

Louis Althusser, Essays in Self-Criticism (1976), "Is it Simple to be a Marxist in Philosophy?"
A - F, Louis Althusser

Source: The Prince (1513), Ch. 3 (as translated by RM Adams). Variants [these can seem to generalize the circumstances in ways that the translation above does not.]: The Romans, foreseeing troubles, dealt with them at once, and, even to avoid a war, would not let them come to a head, for they knew that war is not to be avoided, but is only put off to the advantage of others.
There is no avoiding war; it can only be postponed to the advantage of others.
Context: The Romans never allowed a trouble spot to remain simply to avoid going to war over it, because they knew that wars don't just go away, they are only postponed to someone else's advantage. Therefore, they made war with Philip and Antiochus in Greece, in order not to have to fight them in Italy... They never went by that saying which you constantly hear from the wiseacres of our day, that time heals all things. They trusted rather their own character and prudence — knowing perfectly well that time contains the seeds of all things, good as well as bad.

Source: Are Prisons Obsolete? (2003), Chapter Five

Source: Toward a New Sustainable Economy, 2008, p. 45

"Machinic Desire" (1993), in Fanged Noumena, p. 340 (original emphasis)

That in all cases, for all commodities that serve to provide for the tangible or intangible needs of the consumer, it is in the consumer’s best interest that labor and trade remain free, because the freedom of labor and of trade have as their necessary and permanent result the maximum reduction of price.
... Whence it follows:
That no government should have the right to prevent another government from going into competition with it, or to require consumers of security to come exclusively to it for this commodity.
Source: The Production of Security (1849), p. 3, as cited in: Hans-Hermann Hoppe (2001), Democracy - the God That Failed: The Economics and Politics of Monarchy, Democracy, and Natural Order. Transaction Publishers, p. 271