Menahot, Chapter Four, Mishnah One
In this mishnah we learn of cases where the absence of a part of a certain mitzvah does not prevent the fulfillment of the whole mitzvah.
1) The [absence of the] blue [in the tzitzit] does not invalidate the white, neither does the [absence of the] white invalidate the blue.
2) The [absence of the] hand-tefillin does not invalidate the head-tefillin, neither does the [absence of the] head-tefillin invalidate the hand-tefillin.
3) The [absence of the] fine flour and the oil does not invalidate the wine, neither does the [absence of the] wine invalidate them.
4) The [omission of one of the] sprinklings [of the blood] on the outer altar does not invalidate the rest.
Section one: Tzitzit consist of white and blue strands (Numbers 15:38). If one makes tzitzit with only white or only blue strands, he has fulfilled the mitzvah. Today most people wear tzitzit with only white threads because for many years rabbis did not know how to make the blue threads. However, recently people re-discovered how the blue threads were made. Nowadays, it is becoming increasingly more common to see people with tzitzit made of blue and white.
Section two: Tefillin are worn on the head and arm. These are two separate mitzvoth, so if a person wears one and not the other, he has fulfilled the mitzvah of wearing that particular piece of tefillin.
Section three: A minhah that is accompanied by libations comes with three elements: flour, oil and wine. If one offers one or two of these elements, but not the others, he has fulfilled the mitzvah of that which he offered.
Section four: Some sacrifices require the blood of the animal to be sprinkled on the outer altar, either four times or twice (see Zevahim 5:3-7). If he omits one of the sprinklings he has still fulfilled the mitzvah (see Zevahim 4:1).