Strabon XV 5, 2:

[...] and it was Tryphon (1), together with the worthlessness of the kings who by succession were then reigning over Syria and at the same time over Cilicia, who caused the Cilicians to organise their gangs of pirates; for on account of his revolutionary attempts others made like attempts at the same time, and thus the dissensions of brethren with one another put the country at the mercy of any who might attack it.

The exportation of slaves induced them most of all to engage in their evil business, since it proved most profitable; for not only were they easily captured, but the market, which was large and rich in property, was not extremely far away, I mean Delos, which could both admit and send away ten thousand slaves on the same day [δυναμένη μυριάδας ἀνδραπόδων αὐθημρὸν καὶ δέξασθαι καὶ ἀποπέμψαι]; whence arose the proverb, “Merchant, sail in, unload your ship, everything has been sold [ἔμπορε, κατάπλευσον, ἐξελοῦ, πέπραται].”

The cause of this was the fact that the Romans, having become rich after the destruction of Carthage and Corinth, used many slaves; and the pirates, seeing the easy profit therein, bloomed forth in great numbers, themselves not only going in quest of booty but also trafficking in slaves.
[...]

(Strabo: Geography VI. Ed. by Horace Leonard Jones. Cambridge (Mass.) / London ⁷2006, pp. 326-329)

(1) angenommener Name des Usurpators Diodotos aus Kasiane bei Apameia, zeitweilig Stratege des Demetrios I. Soter, Sohn des Seleukos IV. und Neffe des Antiochos IV. (um 150 v.u.Z.)