Shemot 3:2

בלבת אש means IN A FLAME OF FIRE, i. e. in the very heart of (לב) the fire. Similarly is לב used of inanimate objects in: (Deuteronomy 4:11) “in the heart of (לב) heaven”; (II Samuel 18:14) “in the midst of (לב) the terebinth”. Do not be puzzled by the ת, although the ordinary word for heart, לב. does not require the suffix ת in the construct form, because we have another example of this form, viz., (Ezekiel 16:30) “how weak is thy heart (לבתך)”.‎ מתוך הסנה OUT OF THE MIDST OF A BUSH (a thornbush) — and not from any other tree, in accordance with the idea (Psalms 91:15) “I will be with him in trouble” (Midrash Tanchuma, Shemot 14). אֻכָּל means DEVOURED, eaten. It is of the same grammatical form as, (Deuteronomy 21:3) “which hath not been wrought with (עֻבַּד)”; (Genesis 3:23) “whence he was taken (לֻקַח):

And the angel of the Lord appeared to him in a flame of fire out of the midst of a bush: and he looked, and, behold, the bush burned with fire, but the bush was not consumed.

וַ֠יֵּרָ֠א מַלְאַ֨ךְ יְהֹוָ֥ה אֵלָ֛יו בְּלַבַּת־אֵ֖שׁ מִתּ֣וֹךְ הַסְּנֶ֑ה וַיַּ֗רְא וְהִנֵּ֤ה הַסְּנֶה֙ בֹּעֵ֣ר בָּאֵ֔שׁ וְהַסְּנֶ֖ה אֵינֶ֥נּוּ אֻכָּֽל׃