John Gill Commentary 1 Samuel 24:5

"And it came to pass afterward, that David`s heart smote him, because he had cut off Saul`s skirt." — 1 Samuel 24:5 (ASV)

And it came to pass afterward, that David's heart smote him ,
&c.] His conscience accused him, and he repented of what he had done:

because he had cut off Saul's skirt ;
which though less than what his servants put him upon, and he might have thoughts of doing, yet was considered by him as a great indignity to his sovereign, and therefore sat uneasy on his mind.