This Sunday’s gospel describes how a wealthy man, Zacchaeus, is changed by his encounter with Jesus, promising to give “half of my possessions” to the poor. If he could see his way to giving away a little more than half his fortune, Zacchaeus would qualify for The Giving Pledge, a philanthropic initiative started by Warren Buffett and Bill and Melinda Gates in 2008 to encourage wealthy people to give away a majority of their wealth to philanthropic causes, either during their lives or in their wills.

“We're asking them to be bold. We're asking them to step out and to do something big.”

With an estimated net worth of more than $780 billion, the 156 Giving Pledge participants represent a potentially game-changing force in philanthropy.