P=Priestly Code
"According to the documentary hypothesis, originally proposed by Julius Wellhausen, the Biblical chapters that contain the Jubilee and Sabbatical-year legislation (chapters 25 and 27 of Leviticus) were part of the so-called "P" or Priestly Code that Wellhausen believed represented the last stage in the development of Israel's religion. Wellhausen dated those chapters to a late exilic or post-exilic period though many modern proponents of the Documentary Hypothesis have arrived at different datings."
https://en.wikipedia.org/wiki/Jubilee_(biblical)