What poem is the original source of best laid plans Mice and often go awry?

The phrase "The best-laid plans of mice and men often go awry" comes from Robert Burns' poem "To a Mouse," written in 1785.

Here's the excerpt from the poem:

> "But Mousie, thou art no thy lane,

> In proving foresight may be vain:

> The best-laid schemes o' mice an' men

> Gang aft agley,

> An' lea'e us nought but grief an' pain,

> For promis'd joy!"

The poem is about a farmer who accidentally destroys a mouse's nest while plowing his field. Burns uses the mouse's misfortune to reflect on the unpredictability of life and how even the best intentions can be thwarted by fate.