Luther is famously quoted for his response to the question, “What would you do if you knew the world was going to end tomorrow?” He said he would plant a tree.

The "famously quoted" Apfelbäumgleichnis of Martin Luther is just that— an 'apple tree fable' which Luther never said nor wrote. This is discussed in more detail by Martin Schloemann in his book, Luthers Apfelbäumchen: Ein Kapitel deutscher Mentalitätsgeschichte seit dem Zweiten Weltkrieg (Göttingen: Vandenhoeck & Ruprecht, 1994, 246-251) who also questions whether it was even something that Luther would say.

According to the website, Legenden um Luther: Luther und die Bäume the quote—"Wenn ich wüsste, dass morgen die Welt unterginge, würde ich heute ein Apfelbäumchen pflanzen"—was first attributed in 1944 to Martin Luther.