In an email to staff, the social media firm's new owner said workers should agree to the pledge if they wanted to stay – and if not they would have three months severance.
Musk, who recently took over as the chief executive at Twitter after buying the company, reportedly sent the email to all staff impacted by the potential change at the company according to The Guardian, saying that Twitter "will need to be extremely hardcore" in order to succeed.
Mr Musk, who also heads Tesla and SpaceX, said Twitter will be much more engineering-driven, with employees who write “great code” comprising the majority of the team with the emailing adding: "This will mean working long hours at high intensity. Only exceptional performance will constitute a passing grade.”
Workers were told that they needed to click on a link by 17:00 EST on Thursday, if they want to be "part of the new Twitter" adding "Whatever decision you make, thank you for your efforts to make Twitter successful."
The billionaire, who completed the 44 billion dollar (£37 billion) takeover of the San Francisco company in late October, sacked much of its full-time workforce by email early this month and is expected to eliminate an untold number of contract jobs for those responsible for fighting misinformation and other harmful content.
A number of engineers also said on Twitter they were sacked this week after saying something critical of Mr Musk, either publicly on Twitter or on an internal messaging board for Twitter employees.
Mr Musk has vowed to ease restrictions on what users can say on the platform following his takeover, and indicated that he plans to resume Twitter’s premium service – which grants blue-check “verification” labels to anyone willing to pay eight dollars (£6.70) a month – on November 29.
The billionaire said in a tweet that the relaunch would take place later this month in an effort to make sure the service is “rock solid”.