The thirteen Articles or Principles of Faith formulated according to Maimonides in his Mishnah Commentary to Sanhedrin, introduction to Ch. ix. —which have been accepted by the great majority of Jews and are found in the old prayer books—are as follows:
1. I firmly believe that the Creator—blessed be His name!—is both Creator and Ruler of all created beings, and that He alone hath made, doth make, and ever will make all works of nature.
2. I firmly believe that the Creator—blessed be His name!—is one; and no Unity is like His in any form; and that He alone is our God who was, is, and ever will be.
3. I firmly believe that the Creator—blessed be His name!—is not a body; and no corporeal relations apply to Him; and that there exists nothing that has any similarity to Him.
4. I firmly believe that the Creator—blessed be His name!—was the first and will also be the last.
5. I firmly believe that the Creator—blessed be His name!—is alone worthy of being worshiped, and that no other being is worthy of our worship.
6. I firmly believe that all the words of the Prophets are true.
7. I firmly believe that the prophecy of Moses, our master—peace be upon him!—was true; and that he was the chief of the Prophets, both of those that preceded him and of those that followed him.
8. I firmly believe that the Law which we possess now is the same that hath been given to Moses our master—peace be upon him!
9. I firmly believe that this Law will not be changed, and that there will be no other Law [or dispensation] given by the Creator—blessed be His name!
10. I firmly believe that the Creator—blessed be His name!—knoweth all the actions of men and all their thoughts, as it is said: "He that fashioneth the hearts of them all, He that considereth all their works" (Ps. xxxiii. 15).
11. I firmly believe that the Creator—blessed be He!—rewardeth those that keep His commandments and punisheth those that transgress His commandments.
12. I firmly believe in the coming of the Messiah; and although He may tarry, I daily hope for His coming.
13. I firmly believe that there will take place a revival of the dead at a time which will please the Creator—blessed be His name, and exalted His memorial for ever and ever!
According to Maimonides he that rejects any of these articles is an unbeliever, and places himself outside of the Jewish community.
Often recited daily, these 13 principle of faith fall into three general categories. (a) the nature of belief in God; (b) the authenticity of the Torah, its validity and immutability; and (c) man's responsibility and ultimate reward.(1)
In the second principle Maimonides has replaced in the Hebrew the word for one. This principle is designed to promote God's unity, resembling the prayer found in Deuteronomy 6:4 known as the Shema. Since Maimonides took it upon himself to substitute the hebrew word yachid for echad it causes the reader to see a single unity (such as one person) instead of a compound unity (such as 1 cluster of grapes). The Torah clearly uses the compound unity term instead of the absolute single in its Deut. 6:4 passage. For more on this please read Lessons From The Shema.
1). The Complete ArtScroll Siddur p.178-179.