He lived in the town of Snóksdalur in Dalasýsla county and played an important role in the Battle of Sauðafell and the Lutheran Reformation in Iceland.
Daði was a son of the farmer Guðmund Finnsson and Þórunn Daðadóttir, who was related by marriage to Torfi Arason, the king's representative (hirðstjóri) for the north and west of Iceland.
Guðrún's brothers Marteinn Einarsson, the second Lutheran bishop of Iceland, and the sýslumenn Pétur [is] (who plays an important role in the ensuing struggle because in "his travels on the continent had learned some of the art of fortification.
[4] Catholic Bishop Jón Arason, who strenuously opposed efforts to promote Lutheranism in Iceland, considered Daði and Gleraugna-Pétur as his main opponents.
[6][7] Daði continued his life as a wealthy man, holding numerous properties and a large number of cattle, as well as six ships.