A stallion is like a mocking friend; he neighs under every one who sits on him: The Greek text of the first line is not certain and the meaning is not clear, but the Hebrew is helpful. The whole verse in Hebrew reads “A friend who cannot be relied upon is like a saddled horse; he neighs under everyone who is kind to him [literally, under anyone who loves him].” The author is talking about unreliable friends. You can’t count on them because they’ll respond to anyone who is friendly to them. They’re like horses that are saddled and eager to run; it makes no difference who gets on them—they’re ready to go. This approach for the verse could work:

• An unreliable friend is like a horse, [saddled and] eager for a run, that whinnies [happily] for anyone who shows him affection. *
* Hebrew: An unreliable friend … affection; Greek: A stallion is like a mocking friend; he neighs under anyone who sits on him.

Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on Sirach. (UBS Helps for Translators). New York: UBS, 2008. For this and other handbooks for translators see here.