One does not read a story by starting halfway through the book, jumping to the last chapter and then wrapping it up on page one. That would be very confusing. The message Jesus taught started at the beginning and then worked its way through the Bible to a satisfactory completion. The two men got the whole story the whole picture. In starting at the beginning, Jesus would have been teaching the book of Genesis.
Genesis is the foundational book of the Bible.
In the first few chapters we learn how the universe came into existence, how life all began, where man came from, the origins of evil, language, government, nations, religions and so on. Author and scientist, Henry Morris, lists 14 major topics 5 that have their foundations in Genesis. If you haven t read Genesis then the rest of the Bible is very perplexing. Rather, you begin with basic numbers, and move from the simple to the complex. If you skip the fundamentals, even elementary algebra will be beyond your grasp.