Samaritan Pentateuch - (Easton's Bible Dictionary)
On the return from the Exile, the Jews refused the Samaritans participation with them in the worship at Jerusalem, and the latter separated from all fellowship with them, and built a temple for themselves on Mount Gerizim. This temple was razed to the ground more than one hundred years B.C. Then a system of worship was instituted similar to that of the temple at Jerusalem. It was founded on the Law, copies of which had been multiplied in Israel as well as in Judah. Thus the Pentateuch was preserved among the Samaritans, although they never called it by this name, but always "the Law," which they read as one book. The division into five books, as we now have it, however, was adopted by the Samaritans, as it was by the Jews, in all their priests' copies of "the Law," for the sake of convenience. This was the only portion of the Old Testament which was accepted by the Samaritans as of divine authority.
The form of the letters in the manuscript copies of the Samaritan Pentateuch is different from that of the Hebrew copies, and is probably the same as that which was in general use before the Captivity. There are other peculiarities in the writing which need not here be specified.
There are important differences between the Hebrew and the Samaritan copies of the Pentateuch in the readings of many sentences. In about two thousand instances in which the Samaritan and the Jewish texts differ, the LXX. agrees with the former. The New Testament also, when quoting from the Old Testament, agrees as a rule with the Samaritan text, where that differs from the Jewish. Thus Ex. 12:40 in the Samaritan reads, "Now the sojourning of the children of Israel and of their fathers which they had dwelt in the land of Canaan and in Egypt was four hundred and thirty years" (comp. Gal. 3:17). It may be noted that the LXX. has the same reading of this text.