John Gill Bible Commentary

At the brightness that was before him, The lightning that came out of the thick clouds; which may denote, either the coming of Christ to take vengeance on the Jewish nation, which was swift and sudden, clear and manifest; or the spreading of the Gospel in the Gentile world, in which Christ, the brightness of his Father's glory, appeared to the illumination of many; see Mat 24:27; and both may be intended, as the effects following show; his thick clouds passed; that is, passed away; the gross darkness, which had for so many years covered the Gentile world, was removed when God sent forth his light and truth; and multitudes, who were darkness itself, were made light in the Lord; hail stones and coals of fire; the same Gospel that was enlightening to the Gentiles, and the savour of life unto life unto them, was grievous, like hail stones, and tormenting, scorching, irritating, and provoking, like coals of fire, and the savour of death unto death, to the Jews; when God provoked them, by sending the Gospel among the Gentiles, and calling them: or these may design the heavy, awful, and consuming judgments of God upon them, which are sometimes signified by hail storms; see Rev 8:7. In Sa2 22:13, it is only, "through the brightness before him were coals of fire kindled".