Who makes his angels spirits; his ministers a flaming fire:
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Augustine of Hippo
AD 430
3. "Who maketh spirits His angels, and flaming fire His ministers" (ver. 4): that is, those who are already spirits, who are spiritual, not carnal, He maketh His Angels, by sending them to preach His gospel. "And flaming fire His ministers." For unless the minister that preacheth be on fire, he enflameth not him to whom he preacheth.
Fire. The elements execute his will, (Calmet) or rather, as the apostle, and Chaldean, intimate, the angels do this (Berthier) with zeal and activity, (Hebrews i. 7.; Haydock) and ease. (Worthington)
Some would attribute to the angels some sort of light bodies, and Grotius attempted to revive this opinion, which never could prevail over the contrary one, which is universally received. (Calmet)