Judges 6:20
And the angel of God said unto him, Take the flesh and the unleavened cakes, and lay them upon this rock, and pour out the broth. And he did so. And the angel of God said unto him, Take the flesh and the unleavened cakes, and lay them upon this rock, and pour out the broth. And he did so.
Israel's history moved in a repeated cycle of backsliding and chastisement, confession and deliverance, and from time to time God raised up faithful and valiant men to put down idolatry and deliver Israel from their enemies, and Gideon belongs to that story. The angel of God directed him to lay the flesh and the unleavened cakes upon the rock where he had appeared and to pour out the broth, commanding an offering of sacrifice there, and Gideon obeyed and did so. The prepared food was not received as a meal to be eaten. The angel touched the offering with his staff, and fire burst and rose from the rock and consumed it as a sacrifice.
This consuming of the offering was the sign Gideon had asked for and sought. It confirmed the divine identity and presence of the messenger, answered his request for assurance, and showed the message was from heaven. The heavenly visitor thus revealed was Christ, the Son of God.
The command to sacrifice on the rock did not appoint Gideon to serve as a priest and did not authorize him to establish a new place and system of worship there. His later assumption that it did, and his subsequent actions in that line, lacked divine sanction.