Thor and Harbard, an illustration by Franz Stassen in Die Edda: Germanische Götter- und Heldensagen by Hans von Wolzogen, published in 1920. Thor holding Mjölnir has a duel of wits with the ferryman Harbard, here seen holding an oar or push pole for his boat; they hold their conversation across a sound or river from one another, which is for the better as the insults hurled back and forth test tempers, especially Thor’s.
This conversation is depicted in the poem Hárbarðsljóð (Har-bards-il-yod or Har-barths-il-yoth; The Poem of Harbard), one of many of those collected in the Poetic Edda. It’s a well-known example of a form known as flyting, in which two characters exchange insults; flyting is popular in the Eddas and throughout Norse literature. Flyting is a great way to get to know characters better, as is done here in Hárbarðsljóð; as one character insults another for his (almost always his) exploits in the mythological world, we learn what others think of that character’s actions. Sometimes the insults are about stories we’ve already heard and sometimes the insults reference events that aren’t mentioned anywhere else, but they give us additional information about both characters in the dialogue and help to confirm various aspects of stories all throughout the mythology.
In the case of Hárbarðsljóð in particular, we have some interesting things to learn about Greybeard the ferryman. Many of his exploits are the same as Odin’s, but his perspective also matches that of Loki, and he uses one of the best-known attestations for Sif, that she was unfaithful to Thor, that only comes up otherwise in Lokasenna, a particular Loki spotlight. But between the various descriptions of the character, his listed activities, and most persuasively, Odin listing one of his aliases as Harbard in Grimnismál, we can confidently take Odin to be the author’s intended sparring partner for Thor.
Outside of the flyting form, though, this poem has little in the way of meter or structure, and is nearly conversational (málaháttr style); it may be easier to read (with some annotations for those less familiar with Norse mythology) than many of the poems which stick to a strict meter.
It is also a great poem to read just to see how Thor responds when the ferryman calls him a coward.
It’s also worth noting as a post-script that the television series Vikings included the character Harbard for a three-episode arc in season three. Played by Kevin Durand, Harbard was mysterious, enchanting, and wise in a way beyond that of most men. Whether Durand was in fact playing Odin on yet another trip to find a way to avoid Ragnarök, [spoilers].