What is the significance that they went b'Neshef (at the beginning of the night)?
Malbim: This was to fulfill Elisha's prophecy "ka'Es Machar" (like this time, tomorrow). Had they waited until morning, until they would tell Beis ha'Melech [and they would send men on horses to check
Presumably, the men went when it first became light. They were concerned for an ambush, and one cannot see well at night. (PF)