Halakhah zu Jehoschua 3:19

That is that He commanded the priests to carry the ark on their shoulders, when we want to move it from place to place. And that is His saying, "they bore it on their shoulders" (Numbers 7:9). Even though this command came to the Levites at that time, that was in fact because of the paucity (at that time) of priests who were [actually] obligated with the commandment. If so, the commandment is obligatory on the priests; and they would be the ones to carry it, as it is explained in the Book of Joshua (Joshua 3:6) and in the Book of Samuel (II Samuel 15:25). And when David commanded that the ark be carried the second time, he said in Chronicles (I Chronicles 15:15), "The Sons of Levi carried the Ark of God by means of poles on their shoulders, as Moshe had commanded, in accordance with the word of the Lord." And likewise when it mentions the divisions of the priests into twenty four watches in Chronicles, it states (I Chronicles 24:19), "According to this allocation of offices by tasks, they were to enter the House of the Lord according to the ordinance given to Aharon their father, as the Lord, God of Israel, had commanded him." The Sages, may their memory be blessed, explained that this hints to the service of the priests being to carry the ark on the shoulder. And that is (what is meant by), "as the Lord, God of Israel, had commanded him." And the language of Sifrei is "'According to the ordinance, etc., as the Lord had commanded him' - where did He command him? 'But to the Sons of Kehat he did not give any; since theirs was the service of the [most] sacred objects, they bore it on their shoulders.'" Behold it has been made clear to you that this commandment is included in the commandments. (See Parashat Nasso, Mishneh Torah, Vessels of the Sanctuary and Those who Serve Therein 2.)

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.

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.