Albert Barnes Commentary 2 Samuel 21:1

"And there was a famine in the days of David three years, year after year; and David sought the face of Jehovah. And Jehovah said, It is for Saul, and for his bloody house, because he put to death the Gibeonites." — 2 Samuel 21:1 (ASV)

There is no note of time whatever, nor any clue as to what part of David’s reign the events of this chapter ought to be assigned.

Enquired of the Lord - The Hebrew is “sought the face of the Lord,” a phrase quite different from that so often used in Judges (for example, Judges 1:1) and the Books of Samuel. This probably indicates that this chapter is from a different source. This inference agrees with the indefinite phrase “in the days of David” and with the allusion to the slaughter of the Gibeonites, which has not been narrated elsewhere.

And for his bloody house - This literally means “the house of blood,” that is, the house or family upon which rests the guilt of shedding innocent blood.