Albert Barnes Commentary 1 Samuel 1:26

"And she said, Oh, my lord, as thy soul liveth, my lord, I am the woman that stood by thee here, praying unto Jehovah." — 1 Samuel 1:26 (ASV)

As your soul lives - This oath is unique to the Books of Samuel, in which it occurs six times, and to the Books of Kings, in which, however, it is found only once. See the note on 1 Samuel 1:11.