Musk declined an invitation to the oil fund's investor conference with a dinner invitation from the fund's manager Nicolai Tangen in Oslo in October.
"When I ask you for a favor, which I very rarely do, and you say no, then you shouldn't come and ask me for one until you've done something to change that" Musk writes in a text message to Tangen, as financial newspaper E24 reports.
This is a text message that the newspaper has obtained with the support of the Norwegian principle of public access to information.
Musk also writes to Tangen that, roughly translated, friendship is determined by what one does or does not do for each other.
The oil fund owns around one percent of the shares in Tesla and is thus the company's seventh largest shareholder. In June last year, the fund voted no to the compensation package for Musk, the largest in American business history, valued at tens of billions of dollars. An American judge has also ruled against it twice.
The package was designed as early as 2018 and consists mainly of stock options. Therefore, it varies with stock prices – after Tesla's surge, it is now valued at around 100 billion dollars, well over 1,000 billion kronor. But so far, Musk has not received final approval for the package.