Is billionaire Elon Musk breaking his promise to sell all his possessions and houses? Tesla's CEO has pulled his $37.5 million California mansion off the market after vowing to ditch most of his material wealth last year.

It appeared that Musk was making good on his pledge to offload all his houses. In June, the entrepreneur announced that he successfully sold most of his $100 million property portfolio, except one. The remaining property was a sprawling estate located on the San Francisco Peninsula that Musk said he rented out for events.

But Musk promised to sell his final house, saying in June, "Decided to sell my last remaining house," but that it "Just needs to go to a large family who will live there. It's a special place."

RELATED: Tristan Thompson Sells House He Shared With Khloe Kardashian For $2.5 Million

Musk put the sprawling 1961 estate up on the market for $37.5 million. He purchased it for just over $23 million in 2017 from Christian de Guigné IV, an aristocratic family who owned it for over a century. The home has an 11-car garage, a ballroom, ten bathrooms for just six bedrooms, and quick access to hiking trails, and a nearby private jet center.

Musk currently lives in a tiny prefab home worth $50,000 in Boca Chica, Texas, that he rents from SpaceX, his aerospace company.

But according to Business Insider, the house was only briefly for sale, and the listing was removed on September 11th. They also claim that there was no active push to sell the property, as it was listed without an agent.

It is not known why Musk changed his mind about selling this house, but he has revealed what drove him to liquate most of his assets. In an interview with Mathias Döpfner, CEO of the publisher Axel Springer, Musk revealed that he had an ambitious plan: he wants as much capital as possible to fund a Mars colony.

"It's going to take a lot of resources to build a city on Mars," Musk told Döpfner. "I want to be able to contribute as much as possible to the city," he continued. "That means just a lot of capital."

Musk said that he wanted to make it clear that he was serious about this plan. "And it's not about personal consumption. Because people will attack me and say, oh, he's got all these possessions. He's got all these houses. OK, now I don't have them anymore."

READ NEXT: Ellen DeGeneres Spends $8.5 Million On A 'Fixer-Upper' Mansion

Sources: Business Insider, News18