"I want to repeat with a little more emphasis something I already said: don't stress about work."

That was the message from Slack CEO Stewart Butterfield in an all-staff memo, which he revealed on Twitter on Wednesday.

As the COVID-19 pandemic spreads throughout the United States and the world, Butterfield told employees on Friday (via Slack of course), "We got this. Take care of yourselves, take care of your families, be a good partner. It is fine to work irregular or reduced hours. It is fine to take time out when you need it," he said.

TWEET message

Butterfield said he has seen colleagues' children on video calls, and "that's as it should be. We can afford to be a little more casual right now and everyone is going to be understanding and tolerant — we're all people, and we're all in this together," he said.

His message to staff comes as the pandemic has ushered in a period of rapid growth for the messaging app company. As businesses around the world quickly transitioned to remote work to "flatten the curve" of coronavirus' spread, Slack became an increasingly essential communication tool and landed big accounts, Butterfield said.

TWEET showing growth

Slack has more than 110,000 paying customers, and a market capitalization of $15.9 billion as of the end of the trading day on Thursday. Currently, 100% of Slack's more than 2,000 employees in 18 offices around the world are working from home, a spokesperson for the company tells CNBC Make It. Employees were given a $500 stipend to make their work-from-home arrangements comfortable and will not be charged for sick days through April 15, the spokesperson said.

During the worst pandemic in modern history and record-breaking volatility in the market, how company executives react will be scrutinized, according to Mark Cuban.

For one thing, it's important for business owners to not send their employees back to work too soon the billionaire entrepreneur and star of ABC's "Shark Tank" told CNBC on Wednesday.

"Not only is it a safety issue, it's a business issue," Cuban said on CNBC's "Markets in Turmoil" special.

"How companies respond...is going to define their brand for decades. If you rushed in and somebody got sick, you were that company. If you didn't take care of your employees or stakeholders and put them first, you were that company," he said.

In particular, sending employees back to work too soon could be "unforgiveable" to younger Americans, he said.

"So not only is it smart to take care of your employees, but it's also good business and that's the way I'm looking at it," Cuban said.

See also:

Bill Gates: If I were president, this is what I would do now to fight coronavirus

Look inside the hospital in China where coronavirus patients were treated by robots

Andrew Yang's nonprofit is giving away over $1 million in free cash in response to the pandemic