“in the days of David.” The time of this famine is not given. Many commentators think that this is fairly early in David’s reign.
“the House of Blood-guilt.” “The House of Blood-guilt” is set in opposition to the “House of Saul,” and further describes it. Thus, in God’s eyes, “the House of Saul” was also “the House of Blood-guilt,” and Saul’s house certainly had much blood-guilt associated with it. Besides putting Gibeonites to death, something that is not recorded in the Word, Saul put to death an entire village of priests (1 Sam. 22:16-19); tried to kill David; tried to kill his own son and crown prince Johnathon (1 Sam. 20:33), and almost certainly put to death others who are not recorded in the Bible. Then again, when called upon to kill the Amalekite Agag, an enemy of Yahweh, Saul spared him and Samuel had to do it (1 Sam. 15:20, 33).
For the translation “blood-guilt” see HALOT Hebrew-English Lexicon; the Schocken Bible by E. Fox; and the Keil and Delitzsch Commentary on the Old Testament.