Adultery was acceptable for Viking men, but not their wives
Many Norse men adored their wives, judging by the last words of one man just before he was hung:
” Happy am I to have won the joy of such a consort; ” said the condemned man of his wife. “I shall not go down basely in loneliness to the gods of Tartarus. So let the encircling bonds grip my throat in the midst; the final anguish shall bring with it pleasure only, since the certain hope remains of renewed love, and death shall prove to have its own delights. Each world holds joy, and in the twin regions shall the repose of our united souls win fame, our equal faithfulness in love “(Saxo Grammaticus)
Sadly, however, not everyone practiced “faithfulness in love” The basic requirement of a Norse man was to produce children with his wife. He was not, however, obliged to be faithful. Norse men could keep concubines known as frilles– lower status women who they did not marry and who lived with the man and his wife. According to Adam of Breman, a man could keep as many frilles as he could afford. Society regarded any children from these liaisons as legitimate.
Norse men also kept bed slaves. These unfortunate women had little choice in whether or not they lay with their master. Nor was it a great advantage to be the master’s favorite. Ibn Fadlan described witnessing a Viking funeral where the favored bed slave of the deceased man was killed to accompany him to the afterlife. However, the one taboo liaison for a Norseman was to lie with another man’s wife. For this, he could be fined or killed.
Wives, however, were expected to remain faithful, probably because of the possibility of falling pregnant with a child that was not her husband’s. It’s unlikely that every wife did remain constant. However, if anyone caught a woman being unfaithful, the penalties varied. At best, her hair would be cut off. At worst, she could be divorced or fined- or killed. Adam of Breman even states that she could be enslaved.