Harris Wofford, the longtime national-service advocate and former U.S. senator from Pennsylvania, was a co-sponsor of the 1994 law that designated Martin Luther King’s Birthday a day of service.

On the Case Foundation’s blog, Mr. Wofford recalls the philosophy behind the move: “What would Martin have wanted it to be? Anyone who knew him or marched with him or read or heard his words knows that he would not have wanted it to be a day for rest, recreation, shopping, or just doing nothing.”

He notes that participation in the day of service, which this year will take place on Monday, has grown each year, with backing from Presidents Bush, Clinton, and Obama.

But he urges people to remember “the full-bodied” Martin Luther King Jr. — “the King not only of constructive service, but the King of political action and social invention that focused on the campaigns for the civil-rights acts of 1957, 1964, and 1965.”

People who want to follow his example should go beyond days of service, he says, and make “long and deep commitments” to the years of working together that will be needed to bring about equal opportunity and “build the institutions of education, health care, full employment and self-government necessary to solve our most important social problems.”