Albert Barnes Commentary 1 Samuel 6:15

"And the Levites took down the ark of Jehovah, and the coffer that was with it, wherein the jewels of gold were, and put them on the great stone: and the men of Beth-shemesh offered burnt-offerings and sacrificed sacrifices the same day unto Jehovah." — 1 Samuel 6:15 (ASV)

The word “Levites” here probably means priests (Exodus 4:14), sons of Levi, since Bethshemesh was one of the cities of the priests (Joshua 21:13–16). The burnt offering of the cows was not, in any sense, the offering of the men of Bethshemesh, but rather of the Philistine lords to whom the cart and the cows belonged. The Bethshemites themselves, however, as a sign of their gratitude for such an extraordinary mercy, now offered both burnt offerings and sacrifices—probably peace offerings—and doubtless feasted together with great joy and gladness (see 1 Kings 8:62–66; Ezra 6:16–17). There is nothing in the text to indicate that these sacrifices were offered in any way other than the appointed way by the priests.