Albert Barnes Commentary 2 Samuel 21:6

"let seven men of his sons be delivered unto us, and we will hang them up unto Jehovah in Gibeah of Saul, the chosen of Jehovah. And the king said, I will give them." — 2 Samuel 21:6 (ASV)

Seven men - Seven was a sacred number not only with the Hebrews but with other Eastern nations (Numbers 23:1, 29), and is therefore used on this occasion when the judicial death of Saul's sons was a religious act intended to appease God's wrath for the violation of an oath (Numbers 25:4).

Whom the Lord did choose - Rather, “the Lord’s chosen,” or elect. The same phrase is applied to Moses (Psalms 106:23), to the Israelites (Isaiah 43:20), and to Christ (Isaiah 42:1).