This is nothing - I have always been just a bit missing - nice thing Grace - you left out the easiest bit
 
 
Here is the missing part.

Litlu síðar fundust þeir Njáll.
A little afterwards they met Njal
 
 Njáll bað Gunnar vera varan um sig,
Njal asked (warned) Gunnar to watch himself (where he was going)
 
kvað sér
sagt að þeir undan Þríhyrningi ætluðu að fara að honum
he declared it was said to him that those from under "Three Horns" intended to go for him (might Three Horns be a group of mountain peaks)
 
og bað hann aldrei
fara við fámenni og hafa jafnan vopn sín.
and advised him never to travel (only) with a few men and
always (travel) with arms
 
Gunnar kvað svo vera skyldu. Hann
sagði Njáli að Ásgrímur hefði boðið honum heim "og ætla eg að fara nú í
haust."
Gunnar declared (it) should/would be (so).
He said (to ) Njal that Asgrim had invited him to his (Asgrim's) home "and I
intend to go now in (the) Autumn"

"Lát þú enga menn vita," segir Njáll, "áður þú ferð eða hversu lengi þú ert
í brautu. En eg býð þér þó að synir mínir ríði með þér og mun eigi þá á þig
ráðið."
" You let (imperative ?) no men know" says Njal "either before you go or how
long you are to be away, and I offer you and my sons as well to ride with you  and you will not then be attacked"

Réðu þeir það þá með sér.
Then they planned it between them
 
Grace - ? I thought that the  I was the subject - Njal being speaking  I offer to you - (and my boys) etc etc
I am glad we got this bit - it does explain why  Gunnar's Brother was wishful to let Njal & Co know of the journey
Thanks Grace - that clears things up for me
Kveðja
Patricia
PS Where you say Agli - at the end this should be IMO - to Egil (Agli is the dative - acc. or something of Egil)