"God is pure being: matter is a compound of being and nothingness" 

From "Dialogues" on the psychology of mysticism - Leibniz

Gottfried Wilhelm Leibniz (1646-1716) is a German philosopher and mathematician born at Leipzig and died in Hanover.After completing his philosophical and legal education at Leipzig and Altdorf, Gottfried Leibniz spent several years as a diplomat in France, England, and Holland, where he became acquainted with the leading intellectuals of the age. He then settled in Hanover, where he devoted most of his adult life to the development of a comprehensive scheme for human knowledge, comprising logic, mathematics, philosophy, theology, history, and jurisprudence. His place in the history of the philosophy of mind is best secured by his pre-established harmony, that is, there is no mind-body interaction, but only a non-causal relationship of harmony, parallelism, or correspondence between mind and body.  The notion of purity of anything includes within it the notion of the singularity of its substance or matter. For instance, to speak of the ëpurityí of someoneís soul would be to suppose that souls were wholly good and this one had no bad elements. Secondly, the purity of anything includes the idea of the endurance of its substance or matter under all circumstances and over any period of time - that is, to be abundant and infinite. For we cannot call an army brave so long as it behaves bravely in some battle situations and is cowardly in others, nor a politician ëwiseí if they have wise policies on one topic and foolish ones on antoher. Thus, Purity is the Infinity of Singularity. 

In the context of this quotation, the negation of being is nothingness. God as the creator of everything, the source of all being. And God is the sole source that gives being. The concept of God must not include within it the concept of nothingness, but rather uphold the purity of being.