Albert Barnes Commentary 2 Chronicles 31:6

"And the children of Israel and Judah, that dwelt in the cities of Judah, they also brought in the tithe of oxen and sheep, and the tithe of dedicated things which were consecrated unto Jehovah their God, and laid them by heaps." — 2 Chronicles 31:6 (ASV)

The phrase “the children of Israel” in 2 Chronicles 31:5 appears to refer only to the inhabitants of Jerusalem (see 2 Chronicles 31:4). In contrast, the phrase in this verse, “the children of Israel and Judah that lived in the cities of Judah,” seems to refer to the Jews in the country districts and the Israelites who lived among them (2 Chronicles 30:25).

Of these two groups, the first brought both first-fruits and tithes of “all things.” The second group, who had not been included in the command from 2 Chronicles 31:4, brought in first-fruits, paid the tithe of sheep and oxen only, and offered the holy things they had vowed to God.