In the Weonde Song, a spell that's meant to hallow a place for worship accompanied by certain actions, written by Swain Wodening, the text reads (in a rough Modern English translation)
Fire I carry 'round the frith-stead
And bid men the frith to keep
Light I carry for enclosing
And bid ill-wights flee away
Thunor hallow, Thunor hallow
Thunor hallow this holy-stead
The use of fire here is similar to the modern Neopagan practice of sprinkling salt in a circle to create a hallowed space where "ill-wights" (spirits of ill intent) cannot enter. The second verse is almost exactly the same, except that ill-wights is replaced with outlaws. So it's not just meant to keep ill-wights out, but it's also meant to signify to those humans who are unwelcome to stay out. Meanwhile, those within the "frith-stead" are bid to keep the frith. Frith sort of means peace, but not exactly. A frith-stead can be conceptually translated as "sanctuary." Those who are in a frith-stead, or frith-yard, must leave ALL conflicts outside, and ideally shouldn't be antagonizing to others. If there's a ritual going on, it shouldn't be interrupted.
I can't say whether or not fire was used to mark out frith-yards historically speaking. But the practice does make sense, given that during the Oldest Days, the area where the fire's light reached was safe from animals, and everyone could see what was going on.
There's also the case of funeral pyres/open-air cremations. As today, dead people were either buried, burned, or (much less common today lol) deposited in bogs if they were criminals, human sacrifices, or POWs. Unlike today, however, you didn't really get to choose which one you got, as I understand it. The majority of people were buried, and this was the way people would be with their kin after death. Contrary to modern popular belief, Valhalla/Walhall was not the place all pre-Christians wanted to go to before being introduced to the concept of Christian Paradise; people wanted to be with their kin. Walhall was what happened to those who died in battle, far away from their homes and kin, as one of the two potential "compensations", the other being Folkvangr/Folkenfield. It's not super-easy to find information on what specific significance the funeral pyre had compared to being buried; it's not unlikely that it varied from Tribe to Tribe. In Modern pop-culture depictions, however, there's no doubt that it's something given to deeply respected people. In the Yngling Saga, it states that those who are cremated in this way go to Valhalla (no doubt this text was written after Valhalla became thought of as the pre-Christian equivalent to Paradise.) So this fire becomes the gateway to the Gods, as it were.
On a less grim topic, the Hearth was also considered the "heart", the sacred center, of the home. For many, the Hearth was a pit you could walk all around, and where coals were simmered when it was cold. (Those who've played Skyrim know what it looks like.) It was here that all the cooking happened, and where the entire house's warmth came from. Nowadays, this Hearth has split into the fireplace, the stove, the oven, the furnace, and the water heater. A house with a working Hearth is a house with life.