Exodus 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):

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

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.