Why did they need to bring the Aron to the Beis ha'Mikdash?
'Rashi': Menasheh and Amon had removed it and put idols in place of it 1 - "va'Yasem Es Pesel ha'Semel? b'Veis Elokim" (33:7).
'Rashi' citing Yuma 52b: He told the Leviyim to bury the Aron there. Radak - this was lest it be exiled with Yisrael. There was a rock in Kodesh ha'Kodoshim in the west. The Aron was on it, and in front of it was the jar of manna and Aharon's staff. When Shlomo build the Beis ha'Mikdash, he knew that it would be destroyed. He built a place to hide the Aron, in a deep, hidden place. The rock covered the opening 2 . Yoshiyah commanded to bury the Aron, jar, staff and Shemen ha'Mishchah.
Radak: When Menasheh repented and removed the idols, he should have returned the Aron!
Shekalim 6:2: Once, a Kohen noticed that [Bartenura - a rock of] the Mikdash floor was unlike the others. He began telling a colleague, and died before he finished. They knew that surely, the Aron is buried there. Malbim - surely it was buried opposite [under] where it used to be!
What is the meaning of "Ein Lachem Masa ba'Kasef"?
'Rashi': This is a new matter. Now you need not toil to carry matters. You have no excuse not to serve Hashem via singing, and to slaughter and flay Korbanos Pesach of Yisrael. Malbim - you need not carry, like you did in the Midbar. Now you need only serve Hashem and His nation via Avodas ha'Mikdash.
