I don’t blame you for having trouble with this; I think to understand it one needs more context—more of the poem, and some mythological stuff.
I think that Ovid is talking here about Achilles being educated by Chiron the Centaur. The horse-man was a magister poscentis, an authoritative and demanding teacher.
Verber, verberis (n) is an instrument with which to beat someone—we might speak loosely, in this context, of a “rod” or a “cane”. (We are talking here about certain educational methods which are very much out of vogue today).
Iussas is, I think, a participle from the fourth part of iubeo, “to order”.
Sensurus is a future active participle, of sentio, to perceive.
The sense of the whole, then, is something like:
Those hands which Hector was to feel [upon him] he [ille; Achilles] held out for punishment, when ordered, to the authoritative and demanding teacher [Chiron].
That is interesting Inyx. You translated poscente magistro similarly to the way I originally translated it, as the demanding master. If it is dative through, wouldn't it be poscenti?
I had initially thought that it was an ablative of agent, submitted to blows from his demanding master, but finally decided on an ablative absolute. If it is the latter, then the iussas is repetitious.
It's got to be ablative. I'm not sure how to classify it. If it's agency, prose would usually have an
a(b), right? On the other hand "The master being demanding" seems like awkward English. But however one classifies it, the sense is clear enough, is it not?
Perhaps, if we are trying more closely to imitate the Latin syntax, we might instead say (dropping into iambs):
Those hands that Hector was to feel upon
him once were bidden by a Master stern
and proferred out for blows...
I don't think I understand your point about the iussas being redundant. It seems to me that (as the syntax indicates) the poscente describes Chiron, while the iussas describes the hands.
Probably I'm being stupid.
Yes, and it wouldn't seem logical since verberibus is dative already.
I guess it's a simple ablative absolute. I don't see the redundance either...
When his master ordered him to do so (poscente magistro) he would strecht out his hands (praebuit manus) that he was ordered to strech out (iussas)... Ok, sounds a bit redundant after all But not to the point where it wouldn't make sense anymore. It's poetry after all
As pointed out above, the couplet contains three bits of grammar that are translational bugaboos for (modern) English speakers: The ablative absolute, a perfect passive participle apparently "transferred" to the object, and a relative placed before the antecedent. The basic translation crutch for the first two--translate abl. abs as "with <noun> being/having been <verb>", translate ppp. as "having been <verb>"--are extremely stilted renderings, and preserving the order in the third makes for a convoluted sentence in English: "What Hector was about to touch, (his) hands, that man, with (his) teacher demanding, presented having been ordered to the whips." Yikes that's awful; one crutch per couplet is tolerable, three in the same thought is unforgivable.
Translating sentences like this is when students learn to put away their childish things. Yes, iussas modifies manus, but the sentence reads better in English if it modifies ille. The abl. absolute is technically "separate" from all other parts of the sentence, but it's more natral if it's integrated--sometimes temporally/causally by supplying a word like "after" or "since", sometimes more directly, like in Iynx's excellent suggestion utilizing "to". And I have no problem swapping antecedent and relative in an English translation, e.g. "Hector was about to touch hands which...". I'm also not above adding English words that calrify meaning of the more laconic Latin, e.g. the tense order between sensurus erat and praebuit is better shown using a word like "once" rather than a lengthy collection of modals. Putting it all together: "Hector was about to touch hands which he (Achilles) was once ordered to present to his demanding teacher for beatings." The explanatory (Achilles) is probably not necessary if the couplet is translated in context.
Good translation demands a more sophisticated approach that the "fill in the blank" of beginner crutches. It takes practice but it's worth it.
I suppose the ablative simply expresses the means by which they are safe:
"So the they cannot be safe by the flight by which they have been safe, before."
= "So they cannot flee, as they did in the past"
Btw. duces is not dependent on ante here, I think... duces is a nominative agreeing with onerati.
The sentence is to be taken as ibunt ante te duces, qui colla (= collis) onerati catenis sunt