Bill Shillady, who sent Hillary Clinton daily devotionals during her election campaign, has found himself in hot water because one of them used uncredited material from another pastor.

He was searching online for material on the theme, 'It's Friday – but Sunday's coming,' just in case she lost, describing it as 'a familiar adage'.

But where did the adage come from?

It's familiar to a generation of Christian festival-goers from its use by Tony Campolo, who used it to mesmerising effect and wrote a book with the title. But Campolo borrowed it, as he freely admitted, from Shadrach Meschach Lockridge (1913-2000), the dynamic African-American pastor of Calvary Baptist Church in San Diego, California from 1953-1993.

Lockridge was active in the Civil Rights movement and his church hosted Dr Martin Luther King and other prominent leaders of the movement, but it was as a preacher that he was best known. His ministry reached tens of thousands of people and he was widely honoured.

Lockridge's version is hypnotic and compelling, using the rhythms of poetry to convey a deep spiritual truth. It begins: 'It's Friday. Jesus is praying. Peter's a-sleeping. Judas is betraying. But Sunday's comin'.

'It's Friday. Pilate's struggling. The council is conspiring. The crowd is vilifying. They don't even know that Sunday's comin'.

It concludes: 'It's Friday. Jesus is buried. A soldier stands guard. And a rock is rolled into place. But it's Friday. It is only Friday. Sunday is a-comin'!'

But with all the power and wisdom of that sermon, his best-known is 'That's my King', with its ecstatic but carefully-crafted description of the glory of Christ as its climax.