Sanhedrin, Chapter Three, Mishnah Four
Mishnah four lists which relatives are forbidden to testify or act as judges at a trial.
These are the relatives [that are not qualified to be witnesses or judges]:
1) A suitors father, brother, fathers brother, mothers brother, sisters husband, fathers sisters husband, mothers sisters husband, mothers husband, father-in-law, or wifes sisters husbandthem and their sons and their sons-in-law; also the suitors step-son only [but not the stepsons sons].
a) Rabbi Yose said, Such was the mishnah of Rabbi Akiva, but the first mishnah taught: a suitors uncle, or his uncles son, and all that are qualified to be his heir.
2) Moreover all that were kinsmen at the time [are disqualified]; but kinsmen that have ceased to be kinsmen become qualified.
a) Rabbi Judah says: If a mans daughter died and left children, her husband still counts as a kinsman.
Section one: The first section lists relatives who are disqualified from testifying. The list is self explanatory, and only a few require explanation. A mothers husband refers to someone who is not the suitors father. Any son or son-in-law of any of these listed relatives is likewise forbidden to testify. For instance ones fathers brothers son (a cousin) is forbidden to testify. The only exception is that the suitors stepson, i.e. his wifes son from another marriage, is forbidden to testify but stepsons son is allowed.
Rabbi Yose gives us a glimpse into the development of the Mishnah. The previous clause was the mishnah of Rabbi Akiva, who lived from about 50-135 C.E. Rabbi Yose then relates the way it was taught before this time. While there are some legal differences between the two formulations, the most basic difference is that first mishnah used language that approximated Biblical style (see Lev. 25:49). This change from the earlier language to the later style which was more distinct from the Biblical language, may signify the growing independence of the Oral Torah from the Written Torah. It seems likely that in an earlier stage the Oral Torah was usually preserved as an exegesis or midrash on the verses of the Torah. The advantage to this system was that the Torah was a text known to most. The second advantage was that it was clear that Rabbinic law attained its authority by its being an interpretation of Biblical law. However, the biggest detriment was its lack of organization. Many laws appear in parallel forms in several books of the Torah. For instance laws concerning slavery appear in Exodus, Leviticus and Deuteronomy. Laws concerning the redemption of the first born appear in Exodus, Leviticus, Numbers and Deuteronomy. One who wished to know the law would not know where to find it. One of the innovations of Rabbi Akiva was to sort Jewish law into topical tractates. In our mishnah we see that as this processed developed the language of the laws changed from Biblical to Rabbinic Hebrew.
As far as substantive differences between the first mishnah and Rabbi Akivas mishnah. There are three potential differences: his mothers sisters husband, his mothers husband and his wifes sisters husband. These three men are not potential inheritors and therefore could testify according to the first mishnah, but they may not according to Rabbi Akivas mishnah.
Section two: Only if the relative is a current relative may he not testify. If the relationship is by marriage and it is severed through divorce before the trial, the formal relative may testify. Rabbi Judah states that there is one exception to this rule. If a daughter married a man and had children the husband cannot testify, even after the daughter dies. Since the children bind the husband to the grandfather, he is still considered to be a relative.
Questions for Further Thought: