We'll go with [Double AA's][1] Mishne Torah for now.

[Rambam][2]'s [Mishneh Torah][3] was compiled, according to Wikipedia, " between 1170 and 1180 (4930–4940)."

It begins ([Yesodei HaTorah 1:1](http://www.hebrewbooks.org/rambam.aspx?sefer=1&hilchos=1&perek=1&halocha=1)) "**י**סוד **ה**יסודות **ו**עמוד **ה**חכמות." 


  [1]: https://judaism.stackexchange.com/questions/51358/what-is-the-oldest-work-to-incorporate-an-acrostic-of-shem-havaya-in-the-opening?atw=1#comment136187_51358
  [2]: http://en.wikipedia.org/wiki/Maimonides
  [3]: http://en.wikipedia.org/wiki/Mishneh_Torah