What is "ha'Ofel"?
Rashi citing Targum Yonasan: It is a hidden place. Radak - this is like "Afolim" (Shmuel I, 5:6), i.e. hemorrhoids, which are in a hidden place.
Radak: It is a high place; there was a house there. This is like "Ofel va'Vachan" (Yeshayah 32:14), a high place.
Malbim: It was a secure place outside the city.
From whom did he take?
Rashi: He took from Na'aman's two youths.
Why does it say "va'Yifkod ba'Bayis"?
Radak: He left the money there to hide it from Elisha.
Malbim: He pretended that he is the Ba'al ha'Bayis and oversees and commands there. Via this he tricked the youths to return to their way (with Na'aman).
Why did he send the men away?
Rashi: He did not want Elisha to see.
