We may be able quite to comprehend that God can communicate immediately with man, for without the intervention of bodily means He communicates to our minds His essence; still, a man who can by pure intuition comprehend ideas which are neither contained in nor deducible from the foundations of our natural knowledge, must necessarily possess a mind far superior to those of his fellow men, nor do I believe that any have been so endowed save Christ. To Him the ordinances of God leading men to salvation were revealed directly without words or visions, so that God manifested Himself to the Apostles through the mind of Christ as He formerly did to Moses through the supernatural voice. In this sense the voice of Christ, like the voice which Moses heard, may be called the voice of God, and it may be said that the wisdom of God (i.e. wisdom more than human) took upon itself in Christ human nature, and that Christ was the way of salvation.
In Spinozistic terms, the comparison with Moses is very much in Christ's favor. While Moses is regarded as one of the greater prophets in the Tractatus, 'prophet' always has at least a slightly derogatory tone in Spinoza's works; the prophet is always a sort of poor man's imitation of the philosopher. The phrases by which Christ is described here, e.g., "a man who can by pure intuition comprehend ideas which are neither contained in nor deducible from the foundations of our natural knowledge," on the contrary, are in Spinozistic terms high praise indeed. Indeed, there is no one in all of Spinoza's corpus that Spinoza praises more highly.
Now, at first glance it is slightly odd that a Jewish freethinker would rate Christ so highly. At least, one can assume that he doesn't intend to affirm Christianity in so doing, and that raises the natural question of what he does intend. It might be helpful to add to the mix a passage from a letter Spinoza wrote to Henry Oldenburg:
Lastly, in order to disclose my opinions on the third point, I will tell you that I do not think it necessary, for salvation to know Christ according to the flesh: but with regard to the Eternal Son of God, that is the Eternal Wisdom of God, which has manifested itself in all things and especially in the human mind, and above all in Christ Jesus, the case is far otherwise. For without this no one can come to a state of blessedness, inasmuch as it alone teaches, what is true or false, good or evil. And, inasmuch as this wisdom was made especially manifest through Jesus Christ, as I have said, His disciples preached it, in so far as it was revealed to them through Him, and thus showed that they could rejoice in that spirit of Christ more than the rest of mankind. The doctrines added by certain churches, such as that God took upon Himself human nature, I have expressly said that I do not understand; in fact, to speak the truth, they seem to me no less absurd than would a statement, that a circle had taken upon itself the nature of a square.
All of the passages on Christ that we find in Spinoza's have puzzled commentators, and I don't pretend to have a perfect account. But one of the common interpretations seems to fit the evidence in the best way: Spinoza regards Christ as an exemplary predecessor to his own work. After all, one way to regard Jesus is to think of him as a Jew who broke away from the parochial doctrine of the Pharisees in order to teach a universal morality of love of God and neighbor. Given that Spinoza himself is a Jew who breaks away from the parochial doctrines of rabbinical Judaism (the descendants of the Pharisees) in order to teach a universal morality of love of God and neighbor, I would suggest that this is exactly how he views Christ: Christ is the ideal pre-Spinoza.
And everything seems to bear this out. Spinoza obviously has no interest in seeing Christ as the founder of the Christian Church; he considers the Church to be nothing other than the collapse of Christ's pure doctrine into the darkness of superstition and irrationality. Likewise, he holds that many of the terms in which Christ is described can be seen as metaphorical expressions for the summit of philosophical life. (In a sense, this is doing to Christian doctrine what he already thinks the early Christians did to Jewish doctrines, namely, interpret figuratively things that had originally been taken literally.) He very explicitly makes this move in interpretation in another letter when talking about the resurrection of Christ, which he argues is a spiritual resurrection, a metaphor for Christ's "giving by His life and death a matchless example of holiness", and thus rising above the 'dead', i.e., the people of this world (cf. Mt. 8:22); similarly, his disciples are raised from the dead in the sense that they imitate his life of holiness.
Thus Spinoza accepts that Christ is filled with the Spirit of God -- in the sense that the Idea of God dominates his mind. This idea of God can be called divine Wisdom indwelling the man who is Christ, and since Christ's life perfectly expresses this idea, we can say that divine Wisdom took on human nature in him. Christ is the way of salvation in the sense that he lives a life worthy of all imitation, one governed by reason and love of God and neighbor, that rises above superstition to contemplation of nature; and without the divine Wisdom, i.e., the Idea of God, that we can learn from Christ's example, no one can attain to perfect, stable happiness.