Expensive war (or military operations whatever you want to call it) in Yemen, plus falling oil price means KSA have issued bonds for the first time in a long time :

http://www.wsj.com/articles/saudi-arabia-issues-bonds-worth-...

So yes, they somehow need some cash.

What source would you want? Everybody needs money even if they have enough. Please stop this "provide source" movement for obvious things.