After the Philistines wounded Saul, and then he killed himself, the Philistines took his body, beheaded it, and fastened his body to a wall in Beth Shan.

When the inhabitants of Jabesh Gilead heard of this, they no doubt remembered that forty years earlier, Saul had come to their rescue when an enemy threatened to take over their town. Therefore, they went and retrieved the bodies of Saul and three of his sons,

1Sam. 31.13 Then they took their bones and buried them under the tamarisk tree at Jabesh, and fasted seven days (1 Samuel 31.13). 

These men rescued the bodies of the first king of Israel and of his sons. There is no doubt that fasting for seven days was significant to the men of Jabesh Gilead. They observed a perfect number of days in mourning for the dead king of Israel.