Halfdan Egedius: Illustration for Olav Trygvasons saga (1899)
Heitstrenging (pl. heitstrengingar) is an Old Norse practice of swearing of a solemn oath to perform a future action. They were often performed at Yule and other large social events, where they played a role in establishing and maintaining good relationships principally between members of the aristocratic warrior elite. The oath-swearing practice varied significantly, sometimes involving ritualised drinking or placing hands on a holy pig (referred to as a sónargöltr) that could later be sacrificed. While originally containing heathen religious components such as prayers and worship of gods such as Freyr and Thor, the practice continued in an altered manner after the Christianisation of Scandinavia.
Close similarities have been noted between heitstrengingar and Anglo-Saxon oath-swearing and boasting practices such as the beot, with both involving promises to accomplish tasks that would bring great honour if achieved.