Charles Ellicott Commentary 1 Chronicles 12:33

"Of Zebulun, such as were able to go out in the host, that could set the battle in array, with all manner of instruments of war, fifty thousand, and that could order [the battle array, and were] not of double heart." — 1 Chronicles 12:33 (ASV)

Expert in war ... Marshalling (or ordering) battle with all kinds of weapons of war, and falling into rank (la’adôr, forming in line) without a double heart. The expression “falling into rank” occurs only here and in 1 Chronicles 12:38. Nine manuscripts read instead "helping" (la’zôr), and the Septuagint and Vulgate render it similarly. The Syriac has “to make war with those who disputed the sovereignty of David.” The phrase “falling into rank without a heart and a heart,” asserts the unwavering fidelity and resolute courage of these warriors of Zebulun (compare Psalms 12:3, a speech of smooth things with heart and heart they speak; they think one thing and say another; they are double-minded).

The number of warriors assigned to Zebulun and Naphtali has been thought surprising, because these tribes “never played an important part in the history of Israel” (compare, however, Judges 5:18). The numbers given here are, in any event, not discordant with those of Numbers 1:31; Numbers 1:43; Numbers 26:27; Numbers 26:50.