A source for Martin Luther King Jr.’s quote about faith and the staircase?

Martin Luther King Jr. / Wikimedia Commons

“Faith is taking the first step, even when you don’t see the whole staircase.”

When you search for that sentence on Google, you’ll get about 3,700,000 results — most of which attribute the statement (sometimes as a paraphrase) to Martin Luther King Jr. But can anyone find a source for that citation? I have searched on the King Institute web site — probably the most comprehensive collection  “of King’s most significant correspondence, sermons, speeches, published writings, and unpublished manuscripts” — and found nothing resembling that sentence.

Can anyone shed any light on the history of this famous quotation?

Many thanks to Bronwyn for raising this interesting query.

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