Mark Zuckerberg has sold $95 million in Facebook shares, part of a process to fund a philanthropic venture that aims to give away most of the Facebook founder’s wealth in his lifetime.

The sale of the 768,000 shares disclosed Friday makes good on a pledge by the Facebook CEO and his physician wife, Priscilla Chan, to give away 99% of their Facebook shares.

They made the announcement in a letter to their newborn daughter Max in December when their shares were valued at $45 billion.

On Dec 22., Zuckerberg moved 99% of his shares to the Chan Zuckerberg Initiative. He and his wife plan to sell up to $1 billion per year for the next three years, according to Facebook.

The initiative will focus on personalized learning, curing disease, building communities and connecting people, the couple said in December.

The sales were made between May and August, at prices of about $124. Facebook shares (FB) closed Friday at $123.56, up 18% for the year.