Menahot, Chapter Three, Mishnah Seven
The mishnah continues to list mitzvoth in which the absence of one element disqualifies the fulfillment of the entire mitzvah. The mishnah is quite simple to understand. Below I have mostly provided biblical references.
1) Regarding the seven branches of the menorah, the [absence of] one invalidates the others.
2) Regarding the seven lamps on it, the [absence of] one invalidates the others.
3) Regarding the two portions of Scripture in the mezuzah, the [absence of] one invalidates the other; indeed even one letter can invalidate the whole.
4) Regarding the four portions of Scripture in the tefillin, the [absence of] one invalidates the others; indeed even one letter can invalidate the whole.
5) Regarding the four fringes, the [absence of] one invalidates the others, since the four together form one mitzvah.
a) Rabbi Ishmael says: the four are four separate mitzvot.
Section one: Exodus 25:31-32.
Section two: The lamps refers to the cups that held the oil and the wicks.
Section three: The two portions are Deuteronomy 6:4-9, the Shema, and Deuteronomy 11:13-21, Vehaya im Shamoa. If even one letter is missing or not written correctly, the mezuzah is invalid.
Section four: The four portions are: the two portions that are in the mezuzah and Exodus 13:1-10 and Exodus 13:11-16.
Section five: Numbers 15:38 and Deuteronomy 22:12. According to the first opinion, if one corner of the garment does not have tzitzit, then the mitzvah has not been fulfilled. Rabbi Ishmael holds that each corner is its own mitzvah and therefore if one is missing he has fulfilled his mitzvah.