מדרש על ויקרא 23:34

(Devarim 16:13) "The festival of Succoth shall you make for yourself, seven days": Why is this stated? Because it is written (Vayikra 23:34) "the festival of Succoth, seven days, for the Most High," I might think (that it is being made for the L-rd); it is, therefore, written "shall you make for yourself."