Dayus looked at Sam with immense anger and indignation. As soon as Sam changed his staff and replaced it with a dagger he understood what he is doing.
He is showing off his skills. This is the answer to Dayus' claim that Sam is nothing without his tricks.
He is using different weapons to deal with him and with a sword, the staff, and the spear, Sam came out on top on every exchange while Dayus whose only weapon is a spear and his best fighting condition he couldn't win against Sam in even a single exchange.
This made him feel a burning sensation on his face. But he doesn't know whether it is the shame or the kick Sam gave him on the face.
He cannot stand his humiliation and rushed at Sam with his spear.
Sam dodged the lighting spear coming at him and swung his dagger at Dayus who barely managed to dodge.