Prose Edda fragment

Then said Gangleri: "It seems to me that Mjöllnir is mighty indeed, and it was a sorrow for Thor to lose it." And Just-as-High said "You speak wisely. For the Æsir need the hammer of the Odin's son to protect Ásgard. Now, after this, Odin, who is skilled in magic, placed a curse upon Mjöllnir. From that time on, no unworthy man could lift the hammer, and it would remain with Thor."

Now, Gangleri said: "Surely, another might be worthy. Has no man taken Mjöllnir?". Then spoke Third "In this matter only once. I will tell thee. Thor was sent to a ship, that thought, and there he fought a man, not from the Nine Worlds. Thor was struck down, and parted from his hammer, and then Bernstonebit-Bil lifted Mjöllnir. But by the spell of Odin, none may raise the hammer bar those that are worthy. And so seeing that Bernstonebit-Bil was an ally, Thor yielded."

"And now the Æsir can count upon Thor with Mjöllnir, and Bernstonebit-Bil with Stormbrutna."