While recognizing that David might have had good reasons to celebrate the death of Saul, Anglican priest and exegete John Mayer (1583-1664) argues that his mourning was not feigned. Instead, in David’s sorrow, he finds a true and moving prefiguration of Christ’s command to love one’s enemies.

David Foreshadows Christ’s Command to Love Our Enemies

There was great reason for David’s being sorrowful for his dear friend Jonathan and for the people of God, but how he could truly be sorrowful for Saul does not so easily appear. For much good came of Saul’s destruction:

First, an end was put to tyranny under which the commonwealth had suffered. Second, David was rid of his deadly enemy who always fought against his life. And, third, the expected time now came of fulfilling the promise made to David concerning the prophecy of taking the kingdom from Saul.

Yet it is not to be thought that David feigned this great sorrow, even for Saul. For although Saul hated David, David still loved Saul just as Christ bids us to love our enemies. What’s more, as David’s king and father-in-law, he could not but be greatly grieved at the news of Saul’s death.

1-2 Samuel, 1-2 Kings, 1-2 Chronicles, eds. Derek Cooper and Martin Lohrmann, Reformation Commentary on Scripture, OT Vol. V, p. 143.