Albert Barnes Commentary Judges 12:3

"And when I saw that ye saved me not, I put my life in my hand, and passed over against the children of Ammon, and Jehovah delivered them into my hand: wherefore then are ye come up unto me this day, to fight against me?" — Judges 12:3 (ASV)

I put my life in my hands - Compare 1 Samuel 19:5; 1 Samuel 28:21. The phrase expresses the utmost possible risk, knowingly incurred.