Albert Barnes Commentary 1 Samuel 17:25

"And the men of Israel said, Have ye seen this man that is come up? surely to defy Israel is he come up: and it shall be, that the man who killeth him, the king will enrich him with great riches, and will give him his daughter, and make his father`s house free in Israel." — 1 Samuel 17:25 (ASV)

Free in Israel - In all the other fifteen passages where this word occurs, it means free, as opposed to being a slave (Deuteronomy 15:12–13, 18). Here it may imply a freedom from all such services and burdens as are spoken of in 1 Samuel 8:11–17.