Numbers 4:15

“And when Aaron and his sons had made an end of covering the sanctuary, etc.] Not the holy place, nor the most holy place, for these were not covered by them; but “the holy things” in them, as the Septuagint version, the ark, shewbread table, etc. and all “the vessels of the sanctuary”; all appertaining to those holy things, which are before mentioned. Jarchi interprets the “sanctuary”, or the “holiness”, of the ark and altar, and all the vessels of the sanctuary; of the candlestick and the instruments of ministry: as the camp is to set forward; which made the covering of them necessary, in order to their being carried as that moved: after that the sons of Kohath shall come to bear [it]; or…”

“the sons of Kohath shall come to bear it, but they shall not touch any holy thing, lest they die--The mode of transport was upon the shoulders of the Levites (see on Num 7:9), although afterwards wheeled vehicles were employed (Sa2 6:3; Ch1 15:12). And it was allowed to touch the covering, but not the things covered, on the penalty of death, which was inflicted more than once (Sa1 6:19; Sa2 6:6-7). This stern denunciation was designed to inspire a sentiment of deep and habitual reverence in the minds of those who were officially engaged about holy things.”

“Bear it - Upon their shoulders. Afterward the priests themselves, being multiplied, carried these things, though the Levites also were not excluded. They shall not touch - Before they are covered. Numbers 4:16”

“4:15 Aaron and his surviving sons Eleazar and Ithamar had to cover the sanctuary and all the sacred articles completely before the camp was ready to move, with the groups of non-Levitical tribes marching before and behind the Levites who carried the Tabernacle. The royalty of these objects is seen in the symbolic colors of the coverings, and their sacredness underlies the stern warning that even though the Kohathites were the designated handlers, they must not touch the sacred objects, or they would die. Such respect marked the holiness of Israel’s Lord. The dangers of disregarding these instructions are apparent in 1 Sam 6:19-20 and 2 Sam 6:6-7.”

“after that: Num 7:9, Num 10:21; Deu 31:9; Jos 4:10; Sa2 6:13; Ch1 15:2, Ch1 15:15 they shall: Num 3:38; Exo 19:12; Sa1 6:19; Sa2 6:6, Sa2 6:7; Ch1 13:9, Ch1 13:10; Heb 12:18-29 These things: Num 3:30, Num 3:31 Numbers 4:16”

“After the priests had completed the wrapping up of all these things, the Kohathites were to come up to carry them; but they were not to touch "the holy" (the holy things), lest they should die (see Num 1:53; Num 18:3, and comp. Sa2 6:6-7). Numbers 4:16”