> "Fyrir hitt mun þó ganga," segir Gunnar, "og mundi það Njáll ætla og

Helgi vinur minn að eg mundi hafa nokkura vörn í máli með þér Ásgrímur
ef þeir væru eigi við (against)."

> 'For (all) that (it) will still go (ie the challenge stands),' says

Gunnar, `and Njál would expect that, and Helgi my friend, that I would
have some defence in (any) case with you, Ásgrím, if they were not
against (it).'

"...if they were not present [to support the defense themselves]."
Cf. MM & HP.

'fyrir hitt' -- perhaps this use would come under Zoega's 'fyrir' acc.
(13) "in spite of, against", e.g. 'giptast fyrir ráð e-s' "get married
against someone's advice".