Albert Barnes Commentary 2 Kings 25:18

"And the captain of the guard took Seraiah the chief priest, and Zephaniah the second priest, and the three keepers of the threshold:" — 2 Kings 25:18 (ASV)

It was Nebuzaradan's responsibility to select for exemplary punishment the persons whom he regarded as most guilty, either because of the original rebellion or the prolonged resistance. Instead of indiscriminately taking the first people he found, he first selected those who, because of their offices, would likely have had the most authority: the high priest; the second priest (2 Kings 23:4); three of the temple Levites; the commandant of the city; five members of the king’s Privy Council (or seven, see 2 Kings 25:19); and the secretary (or adjutant) of the commander of the army. To these he added sixty others who were considered "princes." Compared with the many occasions on which Assyrian and Persian conquerors put to death hundreds or thousands after taking a revolted town, Nebuzaradan (and Nebuchadnezzar) must be regarded as moderate, or even merciful, in their vengeance .

The three keepers of the door. This should be read as "three keepers," since the Hebrew has no article. The temple doorkeepers in the time of Solomon numbered twenty-four (1 Chronicles 26:17–18), who were probably under six chiefs. After the captivity, the chiefs numbered either six (Ezra 2:42; Nehemiah 7:45) or four (1 Chronicles 9:17).