1)
What was Avner's intent?
1.
Radak: In a playful way, they will fight with their swords to see who knows better the ways of fighting. Chazal (Vayikra Rabah 26:2) said, because he considered blood of the youths 'playing', he was punished and died by the sword.
2.
Malbim: He intended merely to play, to show their strength when wrestling together.
