The Hebrew word pronounced moe-say-raw, meaning correction, or to be restrained, was the name given to the place in the Sinai wilderness (see The Night Crossing and Why Did Paul Say That Sinai Was In Arabia?) where Aaron died. The Hebrew word is rendered into English, in the King James Version, in two ways, "mosera" and "moseroth," as the singular and plural forms of the word (which is not a coincidence, since it reflected the correction and restraint of a single individual, Aaron, who died and was buried there, as well as Israel as a whole who were given to wander in the desert for forty years after they refused to enter the land of Milk and Honey when they were first given the opportunity to do so - see A Journey Without A Destination).
The plural "Moseroth":
"33:30 And they departed from Hashmonah, and encamped at Moseroth. 33:31 And they departed from Moseroth, and pitched in Benejaakan." (Numbers 33:30-31 KJV)
The singular "Mosera," where the Israelites went after Moses was given, at Mount Sinai, the second set of the Ten Commandments (see The Second Tables of Stone) because Moses broke the first set when he came down from Sinai and saw that Aaron had allowed the Israelites to run wild and worship the golden calf:
"10:3 And I made an ark of shittim wood, and hewed two tables of stone like unto the first, and went up into the mount, having the two tables in mine hand [see What Did The Ten Commandments Look Like?]. 10:4 And he wrote on the tables, according to the first writing, the ten commandments, which the LORD spake unto you in the mount out of the midst of the fire in the day of the assembly: and the LORD gave them unto me. 10:5 And I turned myself and came down from the mount, and put the tables in the ark which I had made; and there they be, as the LORD commanded me.
"Mosera: there Aaron died, and there he was buried"
"Mosera," as the place of Aaron's death, was within the area of Mount Hor, "by the coast of the land of Edom"; Aaron was buried there - after the LORD (i.e. Jesus Christ; see Christ The Creator, 'Before Abraham Was, I AM' and 'The God Of The Old Testament') declared that his time of service was completed.
"20:22 And the children of Israel, even the whole congregation, journeyed from Kadesh, and came unto mount Hor. 20:23 And the LORD spake unto Moses and Aaron in mount Hor, by the coast of the land of Edom, saying, 20:24 Aaron shall be gathered unto his people: for he shall not enter into the land which I have given unto the children of Israel, because ye rebelled against my word at the water of Meribah. 20:25 Take Aaron and Eleazar his son, and bring them up unto mount Hor: 20:26 And strip Aaron of his garments, and put them upon Eleazar [see also The Lines Of Eleazar and Ithamar] his son: and Aaron shall be gathered unto his people, and shall die there.
Other verses provide more detail about Aaron's age and year of death.
"33:37 And they removed from Kadesh, and pitched in mount Hor, in the edge of the land of Edom.
While the high priesthood was established with Aaron, it was only after his death that the Levites as a whole tribe were dedicated to the service of the LORD (see also No Levites In The Lost Ten Tribes?).
"10:6 And the children of Israel took their journey from Beeroth of the children of Jaakan to Mosera: there Aaron died, and there he was buried; and Eleazar his son ministered in the priest's office in his stead. 10:7 From thence they journeyed unto Gudgodah; and from Gudgodah to Jotbath, a land of rivers of waters. 10:8 At that time the LORD separated the tribe of Levi, to bear the ark of the covenant of the LORD, to stand before the LORD to minister unto him, and to bless in his name, unto this day. 10:9 Wherefore Levi hath no part nor inheritance with his brethren; the LORD is his inheritance, according as the LORD thy God promised him." (Deuteronomy 10:6-9 KJV)
The deaths of Moses and Aaron were not far apart in time, and both were buried on mountains where they could see, at a distance, the promised land - but neither was permitted to enter, then, because of the same offense that they committed "at the waters of Meribah-Kadesh."
"32:48 And the LORD spake unto Moses that selfsame day, saying, 32:49 Get thee up into this mountain Abarim, unto mount Nebo, which is in the land of Moab, that is over against Jericho; and behold the land of Canaan, which I give unto the children of Israel for a possession: 32:50 And die in the mount whither thou goest up, and be gathered unto thy people; as Aaron thy brother died in mount Hor, and was gathered unto his people: 32:51 Because ye trespassed against me among the children of Israel at the waters of Meribah-Kadesh, in the wilderness of Zin; because ye sanctified me not in the midst of the children of Israel. 32:52 Yet thou shalt see the land before thee; but thou shalt not go thither unto the land which I give the children of Israel." (Deuteronomy 32:48-52 KJV)
Fact Finder: (a) Why was Aaron called by the LORD to assist Moses? (b) Were Moses and Aaron personally prophetic of the Messiah?