2 Kings 25:25
But it came to pass in the seventh month, that Ishmael the son of Nethaniah, the son of Elishama, of the seed royal, came, and ten men with him, and smote Gedaliah, that he died, and the Jews and the Chaldees that were with him at Mizpah.
Cross-reference
2 Kings 25:22 recounts Gedaliah's appointment as governor — the very event that sets the stage for his assassination here.
In Jeremiah 40:16, Johanan warns Gedaliah that Ishmael will kill him, but Gedaliah refuses to believe — directly setting up the assassination here.
Jeremiah 41:1-15 provides the detailed account of Ishmael's murder of Gedaliah and others, the same event described here.
Zechariah 7:5 mentions a fast in the seventh month — the same month Gedaliah was murdered, establishing the fast's origin.
Zechariah 8:19 lists the fast of the seventh month commemorating Gedaliah's murder — directly tied to the event in 25:25.
Jeremiah 40:8 lists the leaders, including Ishmael, who came to Gedaliah at Mizpah — directly preceding the assassination.
Jeremiah 41:1-15 provides the detailed account of Ishmael's murder of Gedaliah and others, the same event described here.
Jeremiah 41:3 gives the same account of Ishmael killing Gedaliah and the Jews and Chaldeans with him.
Jeremiah 41:18 explains that fear of the Chaldeans caused the remnant to flee, motivated by Ishmael's killing of Gedaliah.
Jeremiah 41:15 adds that Ishmael escaped with eight men to the Ammonites after the assassination.