When Moses strikes the rock in the wilderness, it pours out water. When the Angel of Yahweh strikes a rock in Gideon’s presence, it bursts into flame and eats up the sacrificial meat and bread (Judges 6:21).
In both cases, we can say with Paul “the Rock was Christ.” That’s explicit with the Rock in the wilderness (1 Corinthians 10).
When His food is placed in an altar, Yahweh “eats” it in His fiery presence, a sign of acceptance and communion between Yahweh and the worshiper, a sign of covenant renewed. Gideon’s Rock is an altar, Christ the altar, Christ who blazes with the fire of the Spirit, so that He might be consumed and return to the Father.