Albert Barnes Commentary 2 Samuel 21:8

"But the king took the two sons of Rizpah the daughter of Aiah, whom she bare unto Saul, Armoni and Mephibosheth; and the five sons of Michal the daughter of Saul, whom she bare to Adriel the son of Barzillai the Meholathite:" — 2 Samuel 21:8 (ASV)

Rizpah - See the marginal reference. A foreign origin was possibly the cause of the selection of Rizpah’s sons as victims.

Sons of Michal - This is an obvious error for “Merab” (see the note on 1 Samuel 18:19).