CHICAGO (CBS) — A Thanksgiving proclamation signed by President George Washington will be sold at auction in three weeks, but first it’s on display at Christie’s Fine Art Auctioneer in the John Hancock Center.

“His signature is at the bottom, the bottom right,” said Patrick McGrath, a specialist in books and manuscripts for Christie’s.

Washington’s John Hancock, at it were, was affixed on October 3, 1789, proclaiming the first Thanksgiving, after the creation of the U.S. Constitution.

It is a document that’s full of praise for God.

“It’s the most expressive that Washington has ever been about religion. I have read other texts in which he’s mentioned the divine power. He has referred to God (before), but never as strongly or as emphatically as in this document,” McGrath said.

He estimated the document would sell for $8 million to $12 million.

The auction will be held Nov. 14, in New York, the city where Washington signed the proclamation.

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