A particularly large portion (of something), or the largest portion given. A reference to Genesis 43:34, in which Joseph, the son of Jacob who was sold to the Egyptians and became a high-ranking official, treated his former brothers to a feast, with his youngest brother Benjamin receiving a portion (often translated as "mess") five times that of the others. The phrase is used almost exclusively in reference to God or religion. When it comes to the love God gives us, we all have Benjamin's mess: many times more than we might have expected or felt we deserve.
See also: mess