Brothers shall fight
and fell each other,
And sisters’ sons
shall kinship stain;
Hard is it on earth,
with mighty whoredom;
Axe-time, sword-time,
shields are sundered,
Wind-time, wolf-time,
ere the world falls;
Nor ever shall
each other spare.

[Brœðr munu berjask
ok at bǫnum verða,
munu systrungar
sifjum spilla;
hart er í heimi,
hórdómr mikill;
skeggǫld, skálmǫld
— skildir ru klofnir —
vindǫld, vargǫld,
áðr verǫld steypisk;
mun engi maðr
ǫðrum þyrma.]

Poetic Edda (800–1100) Old Norse anonymous collection of poems

Völuspá [Prophecy of the Völva; Prophecy of the Seeress], st. 45 (AD 961) [tr. Bellows (1936)]
    (Source)

The time of Ragnarok. Narrated by Heiðr.

(Source (Old Norse)). Other translations:

Brethren will fight and slay each other;
Kindred will spurn their consanguinity;
Hard will be the world:
Many the adulteries.
A bearded age: an age of swords:
Shields will be cloven.
An age of winds; an age of wolves.
Till the world shall perish
There will not be one that will spare another.
[tr. Turner (1836), st. 44]

Brothers shall fight, and slay each other; cousins shall kinship violate. The earth resounds, the giantesses flee; no man will another spare.
Hard is it in the world, great whoredom, an axe age, a sword age, shields shall be cloven, a wind age, a wolf age, ere the world sinks.
[tr. Thorpe (1866)]; st. 45-46]

Brother will fight brother and be his slayer,
sister's sons will violate the kinship-bond;
hard it is in the world, whoredom abounds,
axe-age, sword-age, shields are cleft asunder,
wind-age, wolf-age, before the world plunges headlong
no man will spare another.
[tr. Larrington (2014), st. 45]

Brothers will battle and slay each other,
cousins will break the bonds of kin;
it’s harsh in the world, great whoredom,
axe-age, sword-age -- shields are cloven --
wind-age, wolf-age, before the world collapses;
no one will show mercy to another.
[tr. Pettit (2023); st. 44]