Albert Barnes Commentary 1 Samuel 10:19

"but ye have this day rejected your God, who himself saveth you out of all your calamities and your distresses; and ye have said unto him, [Nay], but set a king over us. Now therefore present yourselves before Jehovah by your tribes, and by your thousands." — 1 Samuel 10:19 (ASV)

For the use of “thousand” as equivalent to “family,” see 1 Samuel 23:23 and the marginal note on Judges 6:15. In Numbers 1:16, it may mean whole tribes.