Embrios and Idiots, Eremites and Fryars,
White, Black, and Grey,—with all their Trumpery,
Here Pilgrims roam—
—A while discourse they hold,
No fear lest Dinner cool;—when thus began
Who of all Ages to succeed, but feeling
The Evil on him brought by me, will curse
My Head, ill fare our Ancestor impure,
For this we may thank Adam—
The Great Masters in Composition, knew very well that many an elegant Phrase becomes improper for a Poet or an Orator, when it has been debased by common Use. For this Reason the Works of Ancient Authors, which are written in dead Languages, have a great Advantage over those which are written in Languages that are now spoken. Were there any mean Phrases or Idioms in Virgil and Homer, they would not shock the Ear of the most delicate Modern Reader, so much as they would have done that of an old Greek or Roman, because we never hear them pronounced in our Streets, or in ordinary Conversation.
It is not therefore sufficient, that the Language of an Epic Poem be Perspicuous, unless it be also Sublime. To this end it ought to deviate from the common Forms and ordinary Phrases of Speech. The Judgment of a Poet very much discovers it self in shunning the common Roads of Expression, without falling into such ways of Speech as may seem stiff and unnatural; he must not swell into a false Sublime, by endeavouring to avoid the other Extream. Among the Greeks, AEschylus, and sometimes Sophocles, were guilty of this Fault; among the Latins, Claudian and Statius; and among our own Countrymen, Shakespear and Lee. In these Authors the Affectation of Greatness often hurts the Perspicuity of the Stile, as in many others the Endeavour after Perspicuity prejudices its Greatness.
Aristotle has observed, that the Idiomatick Stile may be avoided, and the Sublime formed, by the following Methods. 
First, by the Use of Metaphors [: Such are those of Milton. ]
Imparadised in one anothers Arms.
—And in his Hand a Reed
Stood waving tipt with Fire.—
The grassie Clods now calvd,—
[Spangled with Eyes—]
In these and innumerable other Instances, the Metaphors are very bold but just; I must however observe that the Metaphors are not [so] thick sown in Milton which always savours too much of Wit; that they never clash with one another, which, as Aristotle observes, turns a Sentence into a kind of an Enigma or Riddle;  and that he seldom has recourse to them where the proper and natural Words will do as well.
Another way of raising the Language, and giving it a Poetical Turn, is to make use of the Idioms of other Tongues. Virgil is full of the Greek Forms of Speech, which the Criticks call Hellenisms, as Horace in his Odes abounds with them much more than Virgil. I need not mention the several Dialects which Homer has made use of for this end. Milton, in conformity with the Practice of the Ancient Poets, and with Aristotle’s Rule, has infused a great many Latinisms, as well as Graecisms, and sometimes Hebraisms, into the Language of his Poem; as towards the Beginning of it.