The Torah in Parshas Eikev ascribes the burial of Yosef to the Jewish people even though it was Moshe alone who made sure Yosef’s bones were removed from Egypt and transported to Eretz Yisrael. Rashi explains that “mitzvah nikreis al shem gomra”, it is the completion of the mitzvah which garners credit, and since Bnei Yisrael and not Moshe completed the burial process, they earn the credit.
Someone in shul asked whether this Rashi does not contradict the Rashi in P’ VaEschanan (4:41) which explains that Moshe designated 3 cities of refuge / arei miklat in Eiver haYarden even though those cities would not serve as a refuge until after the additional three cities in Eretz Yisrael were also designated. Moshe wanted to do as much as he could of the mitzvah even if he could not finish the job.
I think there is a difference between the question of who gets credit and the necessity of putting in maximal effort even if one's efforts go unrewarded and unacknowledged. On a deeper level, I think there is perhaps a lomdish distinction between the Rashis. The burial of Yosef called for the accomplishment of a single act; the mitzvah was incomplete until that act is concluded. True, the arei miklat would not serve as refuge until all six cities were designated, but the designation of each individual city was a discrete act and perhaps a mitzvah in its own right.
Carrying this logic a bit further, we can perhaps distinguish two different elements of arei miklat: 1) the shem ir miklat, a status which results from the city being designated; 2) the actual ability of the city to protect a murderer b’shogeg who flees there. The cities Moshe designated fulfilled the former characteristic but not the latter -- they had the status of arei miklat by virtue of Moshe's designation, but did not yet offer protection. Similarly, one might question with respect to other halachos of ir miklat whether they relate to the shem ir miklat or whether they relate to the functional ability of the city to offer refuge. For example, the halacha is that the city of refuge must contain zekeinim, a beis din of some sort (exactly what type is unclear). Is that a defining characteristic of the shem ir miklat, or a condition of the city serving as refuge? The Minchas Chinuch raises a safeik which may hinge on this question: if a murderer flees to a city with zekeinim but then those zekeinim leave, must the murderer now take refuge in a different city? If the presence of zekeinim are a condition of the city serving as refuge, then their absence opens the murderer to fatal harm. However, if the presence of zekeinim serve to establish the shem ir miklat, then perhaps their presence is necessary only at the time of the city’s establishment, but not forever after.