Verse 20: And the angel of God said unto him, Take the flesh and the unleavened cakes, and (Judg. 13:19) lay them upon this rock, and (see 1 Kings 18:33, 34) pour out the broth. And he did so.
[Put them upon that rock] That rock, rough and unpolished, he chooses in the place of an altar. For the Hebrews also were building their altars from mounds and unpolished stones by the commandment of God, Exodus 20:24-26; especially when sudden necessity required an altar and a sacrifice (Bonfrerius). This rock was a type of Christ, 1 Corinthians 10:4 (Lapide).
[And pour out the broth over it] This he willed to be done, either, 1. so that all that had been offered might be consumed. Or, 2. so that he might increase the miracle, so that the fire might leap from the provisions, swimming in broth and aqueous matter, and consume the whole (Bonfrerius). For, although the material was more fatty, yet it was damp and cold (Malvenda). The broth, tepid from the delay, would become cold more quickly from the cold stone (Montanus’ Commentary). Or, 3. from the ancient rite, in which altars were anointed, Genesis 28:18; Exodus 40:9, 10; or, as others maintain, in the place of a drink-offering (Menochius, Malvenda). He commanded there to be flesh and an offering of bread, but the broth of flesh as a drink-offering (Montanus’ Commantary).
Verse 21: Then the angel of the LORD put forth the end of the staff that was in his hand, and touched the flesh and the unleavened cakes; and (Lev. 9:24; 1 Kings 18:38; 2 Chron. 7:1) there rose up fire out of the rock, and consumed the flesh and the unleavened cakes. Then the angel of the LORD departed out of his sight.
[He extended tip of his rod] Or of his travelling staff, which he was carrying in his hand like a traveler (Bonfrerius).
[Fire came up from the rock] Having been divinely sent, as in Judges 13:20 (Grotius).
[And it consumed] Behold the sign that the Angel exhibited to Gideon in answer to his request. He shows that he is an Angel (Lapide). He shows that he is an Angel, and not a man, inasmuch as he had no need of food (Grotius).
Then the Angel of the Lord, etc.: By these things he showed himself to be no man that needed such provisions, but a true angel of God, or the Son of God; and by this instance of his omnipotency, gave the assurance that he both could and would consume the Midianites.
 Hebrew: וַיֹּ֙אמֶר אֵלָ֜יו מַלְאַ֣ךְ הָאֱלֹהִ֗ים קַ֣ח אֶת־הַבָּשָׂ֤ר וְאֶת־הַמַּצּוֹת֙ וְהַנַּח֙ אֶל־הַסֶּ֣לַע הַלָּ֔ז וְאֶת־הַמָּרַ֖ק שְׁפ֑וֹךְ וַיַּ֖עַשׂ כֵּֽן׃
 Hebrew: וַיִּשְׁלַ֞ח מַלְאַ֣ךְ יְהוָ֗ה אֶת־קְצֵ֤ה הַמִּשְׁעֶ֙נֶת֙ אֲשֶׁ֣ר בְּיָד֔וֹ וַיִּגַּ֥ע בַּבָּשָׂ֖ר וּבַמַּצּ֑וֹת וַתַּ֙עַל הָאֵ֜שׁ מִן־הַצּ֗וּר וַתֹּ֤אכַל אֶת־הַבָּשָׂר֙ וְאֶת־הַמַּצּ֔וֹת וּמַלְאַ֣ךְ יְהוָ֔ה הָלַ֖ךְ מֵעֵינָֽיו׃