John Gill Commentary 2 Samuel 18:22

"Then said Ahimaaz the son of Zadok yet again to Joab, But come what may, let me, I pray thee, also run after the Cushite. And Joab said, Wherefore wilt thou run, my son, seeing that thou wilt have no reward for the tidings?" — 2 Samuel 18:22 (ASV)

Then said Ahimaaz the son of Zadok yet again to Joab
He could not be easy, even though a messenger was dispatched, but pressed Joab still:

but howsoever, let me, I pray thee, also run after Cushi ;
only permit me to go after him, though not as a messenger:

and Joab said, wherefore wilt thou run, my son ?
having a great affection for him, and concerned that he should take trouble on him to no purpose:

seeing thou hast no tidings ready ;
no news to carry, but what Cushi is gone with, and so can have no audience of the king, nor any reward from him.