Thanks, couldn't find this. This is essentially a proposal to the court about how the case could be resolved though, not a promise, and he only proposed it after the judge denied his original proposal (https://cdn.arstechnica.net/wp-content/uploads/2026/04/Musk-...), which was "give me $134 billion". I think it would have been a little more credible if he had requested this originally.
Even taking it at face value, it's just an idea for the judge to consider, not legally binding for anybody.