Delaying Mitzvot

1. There is a general rule that one may not pass over or delay doing a mitzvah that comes one's way. According to many poskim this is a Biblical principle, while others hold it is rabbinic.
2. It only applies when one is deciding to do one of two mitzvot. However, if a mitzvah doesn't apply now there's no prohibition to pass over that mitzvah. Similarly, if one is faced with two mitzvot and one only has time to fulfill one of them then there is no prohibition to pass over a mitzvah. Rather one should do the mitzvah according to the following factors:
   1. One should do the mitzvah that is more severe such as tefillin more kadosh than tallit.
   2. If both are equally severe then choose the mitzvah that is more common.
   3. If they are equally common choose the mitzvah that expires first.
      1. If a mitzvah is more severe than another it takes precedence over another less severe mitzvah even if the less severe one expires sooner. For example, if on Erev Yom Kippur someone is in an army that would stop him from doing mitzvot and he can either take guard duty today and then fast tomorrow or take guard duty tomorrow and fulfill tefillin today he should take the guard duty today since the mitzvah to fast on Yom Kippur is more severe than tefillin.
3. There is no consideration of not passing over a mitzvah if he wouldn't be involved in the mitzvah himself. For example, passing over the opportunity to watch a mitzvah so that it would be a greater publicity of the mitzvah isn't a prohibition.
4. If someone can do the mitzvah later in a better fashion then one may delay it and it isn't considered passing over a mitzvah.