Jack Dorsey is pledging $1 billion of his stake in Square Inc.—the mobile payments company he co-founded—to help fund coronavirus relief efforts.

Dorsey, who is CEO of both Square and Twitter, made the announcement on his social platform.

His donation—which he reports is about 28% of his estimated $3.9 billion net worth—is by far the largest yet by an individual. Other top philanthropists include Bill and Melinda Gates, whose foundation committed $100 million to develop a vaccine and support detection, isolation and treatment efforts.

“Why now? The needs are increasingly urgent, and I want to see the impact in my lifetime,” he wrote. “I hope this inspires others to do something similar. Life is too short, so let’s do everything we can today to help people now.”

All of the donations Dorsey makes will be tracked in a publicly available Google sheet. So far that document shows $100,000 has been granted to America’s Food Fund, which was started by Laurene Powell Jobs and Leonardo DeCaprio.