Charles Ellicott Commentary 2 Samuel 4:10

"when one told me, saying, Behold, Saul is dead, thinking to have brought good tidings, I took hold of him, and slew him in Ziklag, which was the reward I gave him for his tidings." — 2 Samuel 4:10 (ASV)

Who thought that I would have given him. —The words thought that I would are not in the original, and the literal translation of the margin is better: “which was the reward I gave him.” This shows very plainly David’s view of the motive which prompted the Amalekite to his lie recorded in 2 Samuel 1:10.