John Gill Commentary 1 Samuel 23:21

"And Saul said, Blessed be ye of Jehovah; for ye have had compassion on me." — 1 Samuel 23:21 (ASV)

And Saul said, blessed [be] you of the Lord
He highly commends them for the offer they made to him, blesses God for them, and desires the blessing of God upon them for it:

for you have compassion on me ;
pitied him on account of the troubles he met with from his son-in-law, were sorry for him, and sympathized with him, which others did not, of which he complained, (1 Samuel 22:8) .