"Don't bluff sir"

A short stacked player raised half his stack from UTG and JC Tran called from two seats along. Everyone else folded and when the flop was about to come down {2-Hearts}

Tran said to his opponent "Don't bluff sir".

UTG checked and Tran bet an amount to commit the player if he called. He folded though and Tran tabled {A-?}

with a big smile on his face.