Twitter‘s remote working will be phased out, according to Elon Musk. Musk, who took over Twitter on October 27, sent his first email to his employees on Wednesday. According to the email’s time stamp, it was sent at 2:39 a.m. ET.

In the email, the billionaire stated that employees would no longer be permitted to work remotely. He stated that Twitter expected employees to work at least 40 hours per week unless they were given permission to work elsewhere, which he would review.

“The road ahead is arduous and will require intense work to succeed,” Musk told Twitter employees.

The CEO of Tesla and SpaceX began the email by saying there was “no way to sugarcoat the message” about the economy and its impact on Twitter, which relies on advertising.

Employees noticed the company’s “days of rest,” implemented by Twitter cofounder Jack Dorsey, had been removed from their calendars days after Musk finalized his deal with Twitter, according to people familiar with the matter. While Dorsey encouraged employees to avoid burnout, employees at Musk’s other companies, such as SpaceX and Tesla, are notorious for working long hours.

The shift in pace at Twitter was highlighted last week when a photo of a manager sleeping on the floor at the company’s San Francisco headquarters was posted on the social media platform.

The letter was previously reported by Bloomberg.

Read the entire email Musk sent to employees below:

Sorry that this is my first email to the whole company, but there is no way to sugarcoat the message.

Frankly, the economic picture ahead is dire, especially for a company like ours that is so dependent on advertising in a challenging economic climate. Moreover, 70% of our advertising is brand, rather than specific performance, which makes us doubly vulnerable!

That is why the priority over the past ten days has been to develop and launch Twitter Blue Verified subscriptions (huge props to the team!). Without significant subscription revenue, there is a good chance Twitter will not survive the upcoming economic downturn. We need roughly half of our revenue to be subscription.

Of course, we will still then be significantly reliant on advertising, so I am spending time with our sales & partnerships teams to ensure that Twitter continues to be appealing to advertisers. This is the Spaces discussion that Robin, Yoel and I hosted today:

[Links to a Twitter Spaces recording called “Elon Q&A: Advertising & the Future.”]

The road ahead is arduous and will require intense work to succeed. We are also changing Twitter policy such that remote work is no longer allowed, unless you have a specific exception. Managers will send the exceptions lists to me for review an approval.

Starting tomorrow (Thursday), everyone is required to be in the office for a minimum of 40 hours per week. Obviously, if you are physically unable to travel to an office or have a critical personal obligation, then your absence is understandable.

I look forward to working with you to take Twitter to a whole new level. The potential is truly incredible!

Thanks,

Elon