The Messenger of the Covenant
The "messenger" is Jesus in his pre-human existence as Michael, sent as
Jehovah's agent. Jehovah did not personally come to the temple — Jesus
came on his behalf, "by means of" agency.
Walk slowly through . Three figures are named: (1) my messenger who prepares the way (John the Baptist — quotes this verse); (2) the Lord (Hebrew ha-Adon, the sovereign Master) whom you seek; and (3) the messenger of the covenant. The first is John, distinct from Jehovah. The Lord and the messenger of the covenant are then put in apposition — the one who suddenly comes to His own temple IS the messenger of the covenant. And the speaker is Jehovah Himself: "the way before me." Jehovah says He is sending a messenger before Him, and that the messenger of the covenant who follows that forerunner is the same Lord coming to His own temple. The text identifies Jehovah's coming with the messenger of the covenant's coming. then identifies that forerunner as John the Baptist, and the one for whom he prepares the way as Jesus. Therefore Jesus is the Jehovah of .
Jehovah said "the way before me." Mark says John prepared the way for Jesus. So when Jehovah came to His own temple, He came as Jesus.
The messenger came on Jehovah's behalf as his agent — it's not Jehovah himself who arrived
The verse will not let you do that. Jehovah is speaking in the first person: "I send my messenger, and he will prepare the way before me." That "me" is the speaker — Jehovah. The forerunner prepares for Jehovah. Then "the Lord whom you seek will suddenly come to HIS temple" — the Lord owns the temple. In the entire Old Testament, whose is the temple? Jehovah's. So the Lord who comes is Jehovah. And the messenger of the covenant in that same sentence is in apposition to "the Lord" — meaning they are the same person. then names the forerunner as John, and the Lord as Jesus. The verse doesn't allow a separate "agent who came instead of Jehovah" — it equates the coming of the Lord with the coming of the messenger of the covenant.
The temple here is Jehovah's earthly organization — Jesus inspecting in 1918
specifies the second temple — the one rebuilt under Zerubbabel, standing in Malachi's day. Jesus literally walked into that temple. Twice he cleansed it. He called it "my Father's house" () and "my house" (). The 1918 "spiritual temple inspection" is read backwards into the text. Read the verse forwards instead: a physical temple, a literal coming, fulfilled when Jesus stood inside Herod's temple.
John the Baptist could be the messenger of the covenant too — there are two distinct messengers in the verse
That collapses the grammar. The forerunner-messenger and the messenger-of-the-covenant are deliberately distinguished by the verse itself: one comes first to prepare, the other comes after and is identified with "the Lord whom you seek." Even your own Watchtower publications acknowledge the messenger of the covenant is Jesus — see Insight on the Scriptures under "Messenger." The question is then unavoidable: if the messenger of the covenant is Jesus, and the messenger of the covenant is "the Lord" coming to "his own temple" announced by Jehovah saying "before me" — then Jesus is the Lord whose temple it is.
Don't argue about whether 1918 happened. Stay on the grammar of Malachi 3:1 itself — Jehovah said "before me," and the messenger of the covenant is the one who comes. The argument is the text, read forward.
Read alongside . Notice that Mark applies Malachi's forerunner prophecy to John the Baptist, and the one for whom the way is prepared to Jesus. Whose way is John preparing? Malachi says Jehovah's. Mark says Jesus'.