Originally Posted by Spinoza, Letter to G.H. Schaller

Further conceive, I beg, that a stone, while continuing in motion, should be capable of thinking and knowing, that it is endeavoring, as far as it can, to continue to move. Such a stone, being conscious merely of its own endeavor and not at all indifferent, would believe itself to be completely free, and would think that it continued in motion solely because of its own wish. This is that human freedom, which all boast that they possess, and which consists solely in the fact, that men are conscious of their own desire, but are ignorant of the causes whereby that desire has been determined.

Originally Posted by Wikipedia

In the last two propositions of Part Two of The Ethics, P48 and P49, he explicitly rejects the traditional notion of free will. In E2P48, he claims:
So from this we get a strong sense of Spinoza's Naturalism, that is, that the natural and human orders are contiguous. With that being the case, human freedom of a kind which would extricate us from the order of physical causes is impossible. However, Spinoza argues, we still ought to strive to understand the world around us, and in doing so, gain a greater degree of power, which will allow us to be more active than passive, and there is a sense in which this is a kind of freedom.