Κοινὰ τὰ φίλων.
Friends have things in common.
Literally, the things of friends are common; in other words, "what's mine is yours, and what's yours in mine." This is the very first item in Erasmus's adages. Erasmus cites a wide variety of Greek sources for this popular saying, including Euripides' Orestes; the saying appears in a conversation between Orestes and his dear friend Pylades. The adjective φίλος is being used substantively, as a noun: "friend." From this same root in Greek we get all the phil- words in English.
Βοιώτιος νοῦς.
The mind of a Boeotian.
This proverbial saying referred to someone who was ignorant or stupid; such was the reputation of people from Boeotia, a region in central Greece. You could also find the sentiment expressed in this form: Ἡ Βοιωτία ὗς, a Boeotian pig. The Greek phrase lives on in French, where the insulting term béotien means someone who is a country bumpkin, unsophisticated (compare the English use of "philistine," lower-case p).
Ἡρακλῆς καὶ πίθηκος.
Heracles and an ape.
The saying is about things that cannot be compared, much like the English saying "apples and oranges." Lucian uses these words to denounce contemporary philosophers in The Fisherman, where he also includes the absurd comparison of a vulture to a nightingale (νῦν δὲ θᾶττον ἂν γὺψ ἀηδόνα μιμήσαιτο ἢ οὗτοι φιλοσόφους).
Πάθει μάθος.
Wisdom (is acquired) by means of suffering.
The words are spoken by the chorus in Aeschylus's Agamemnon, where the word μάθος is a poetic equivalent to μάθησις, "learning, the getting of knowledge, wisdom." The word πάθος (from the verb πάσχω) can simply mean "experience," but it can also have the negative connotation of "suffering." Given that the chorus then goes on to speak about πόνος, "hard work, toil," I opted for "suffering" in the English translation. In addition, Greek πάθος can also mean "emotion, passion," which is the sense it has taken on in the English word pathos, and also in compounds like sympathy and empathy. Compare a saying from an earlier blog post: Τα παθήματα μαθήματα.
Ὅσια κρῖνε.
Choose the things that are holy.
This is one of the Delphic maxims recorded by Stobaeus. The verb κρίνω has a wide range of meaning; often it means "decide," but here, with a direct object, it means something more like "pick out, choose." Note also the circumflex accent for this imperative form: κρῖνε.