Halakhah zu Jehoschua 3:3

And Rabbi Moshe ben Nachman (Nachmanides), may his memory be blessed, wrote (in his glosses to the Sefer HaMitzvot LaRambam on the third Shoresh, s.v. veraiti) that that which the teacher said that the commandment was moved to the Kohanim is not true. God forbid that we should say that any commandment in the Torah changed, that the Levites were disqualified from carrying the Ark forever, and that he explained it well. [As we see that] the Levites carried it in the days of David, as it is stated (I Chronicles 15:26), "And it was in God's assisting the Levites who were carriers of the Ark of the Covenant of the Lord," and it is written (I Chronicles 15:27), "And all the Levites who were carrying the Ark, etc." But in truth, both the Kohanim and Levites are acceptable for carrying the Ark from Torah writ. As they are all called Levites, as it is written (Ezekiel 44:15), "the Levite Kohanim." And so [too,] is it written (I Chronicles 15:14-15), "And the Kohanim and Levites sanctified themselves to bring up the Ark of the Lord, the God of Israel, as Moshe had commanded by the word of the Lord, with the poles on their shoulders." And they said in the Sifrei, "Where did He command [this]? [From the verse] 'And to the sons of Kehat was not given any other, etc.'" - as they are all called the sons of Kehat. And he also wrote [regarding] what Maimonides, may his memory be blessed, wrote that it is elucidated from the Book of Joshua and Samuel, that he did not find this elucidation. Rather, he found the opposite, as it is stated there (Joshua 3:3), "And he commanded the people saying, 'When you see the Ark of the Covenant of the Lord, your God, that is carried by the Kohanim, Levites." Rather, the truth is as we have said, that the whole tribe is eligible to carry the Ark. Moreover, the thing is explicit in Tractate Sotah 33b, where they, may their memory be blessed, said, "How did the Israelites cross the Jordan? Every day the Levites carried the Ark, and on this day it was carried by the Kohanim." That is, on the day that they crossed the Jordan, only the Kohanim carried it, as so is it written (Joshua 3:6), "And Yehoshua said to the Kohanim, 'Carry the Ark of the Covenant'" - so that the miracle would be done by the Kohanim, as they are the holiest members of the tribe.