Leviticus 9:11

And the flesh and the hide he burnt with fire without the camp.

The burning of the flesh and hide outside the camp took place during Aaron's first service as priest after the dedication of the tabernacle. The sacrifices of that day were presented exactly as God had directed. God showed His acceptance of the sacrifice by sending fire that consumed the offering upon the altar. That miraculous fire was a revelation of His glory and a token of His favor.