John Gill Commentary 1 Samuel 15:14

"And Samuel said, What meaneth then this bleating of the sheep in mine ears, and the lowing of the oxen which I hear?" — 1 Samuel 15:14 (ASV)

And Samuel said, what means then this bleating of the sheep
in my ears
For the orders were to destroy all living creatures belonging to the Amalekites, (1 Samuel 15:3) if therefore Saul had performed the commandment of the Lord, as he said he had, where were these sheep Samuel heard bleating?

and the lowing of the oxen which I hear ?
where do they come from? these questions he put to convict him of the falsehood he had delivered; the bleating and lowing of these creatures proved him a liar, and were witnesses of his breach of the divine command; and one would think every bleating and lowing of these must alarm his conscience, unless dreadfully stupefied.