Albert Barnes Commentary 1 Samuel 13:22

"So it came to pass in the day of battle, that there was neither sword nor spear found in the hand of any of the people that were with Saul and Jonathan: but with Saul and with Jonathan his son was there found." — 1 Samuel 13:22 (ASV)

This detail seems to be mentioned here in anticipation of the narrative in the next chapter, in order to enhance the victory gained by the comparatively unarmed Israelites over their enemies through God’s help (1 Samuel 14:23). Due to occasional skirmishes with the Philistines, the necessity of using their arms for domestic purposes, accidental losses, and ordinary wear and tear—coupled with the impossibility of renewing their arms without smiths or forges—the people with Saul and Jonathan became very poorly armed.

Moreover, it has been observed that the Benjamites were more famous for the use of the sling than for any other weapon (Judges 20:16), and this would be an additional reason for the scarcity of swords and spears.