"þurh hwæt," l. 400

I am having trouble getting a good translation out of the following lines:

“Hwæt, we Ebreisce æ leornedon,
þa on fyrn-dagum fæderas cuðon
æt godes earce, ne we geare cunnon
þurh hwæt ðu ðus hearde, hlæfdige, us
eorre wurde.

The line itself is not too difficult, and I think I've toggled everything into place except the prepositional phrase "þurh hwæt" --assuming that it is a prepositional phrase-- Where do these words go? The problem seems to be that the final part of this sentence is already modified within an inch of its syntax, bearing the weight of both "geare" (readily) and "hearde" (sternly, severely).

Checking in with older translations was not very helpful either. Kennedy, my preferred translator (love love his edition of the Cynewulf poems), provides this as a translation:

Lo, we have learned the Hebraic law, which in the days of old our fathers knew, at the ark of the convenant of God, nor know we well (geare) wherefore thus heavily (hearde), O Lady, thou art become wrathful against us (p. 99)

And Bradley gives it like this:

But we have learned the Hebrew law which in days long since our fathers knew at the ark of God, and we do not readily (geare) understand why you, lady, have been so sternly (hearde) angry with us.

In neither case does "þurh hwæt" seem to appear (unless Kennedy's "wherefore" translates it, which I guess could be a possibility). What's more aggravating is that the adjective "hwæt" (meaning "Quick, active, vigorous, stout, bold, brave") does not seem to be declined. If it is prepositional phrase, it means something like "through, or by means of active, quick, or bold men," or could be translated roughly as "quickly, boldly."

I really don't know. Perhaps you have a solution you'd like to share with me?

* Update: Thanks to Paul for pointing me in the right direction *

* And silly me for not remembering that hwæt is a declined form of hwa! *