The People, Yes alludes to what historical document?

The People, Yes is a poem by Carl Sandburg which alludes to more than one piece of rhetoric penned by President Abraham Lincoln. In the first instance, the title and the line "of the people, for the people, by the people" are both clear references to the address delivered by Lincoln at Gettysburg in 1863 when the new Soldiers' National Cemetery was being dedicated. This was a speech that was only two minutes long, which Lincoln himself felt somewhat ashamed of, but it has become one of the most famous speeches in American history.
Toward the end of the poem, we find the following quotation:

I have not willingly planted a thorn
in any man’s bosom.

This is taken directly from one of Lincoln's written works, "Response to a Serenade," which was written in 1864.

After this, we find another quotation, although the poet has slightly amended it. In an 1862 letter to Thomas Durant, who had complained that slaves had been taken away from their masters by the federal government, Lincoln wrote, "I shall do nothing in malice. What I deal with is too vast for malicious dealing." In defense of his own bent toward freeing the slaves, he prevailed upon Thomas Durant in this letter to appreciate the President's position and understand that the winds of change had already been blowing across Europe on this matter. The President had to take the action he felt was right for the country.