When Stephen met his accusers in Acts 6, before finally being killed by them, Luke tells us that those seated in the Sanhedrin looked intently at his face and saw a "face of an angel" (6:15). For some time this verse remained a mystery to me.
According to Darrell Bock, one of the "go-to" commentators on the book of Acts, Stephen had “the appearance of one inspired by and in touch with God” and that it was Luke’s way of saying that Stephen was innocent (pg. 274, Acts). Bock, along with other commentators like Matthew Henry, favors the view that Stephen's appearance is similar to that of Moses’ radiant face in Exodus, or Christ’s transfigured face back in Luke's gospel (c.g. Ex. 34:29-35; Luke 9:29).
Although these parallels have their appeal, I think they the lack the explanatory power for the absence of a typical response (fear/terror) demanded by either Moses-type or Christ-type encounters. Even the angels themselves have had occasions to incite fear in men, especially when the light of God’s glory accompanied them (Luke 2:9). Still, the New Living Translation dynamically reads, “[Stephen’s] face became bright as an angel’s.” If this was true, why weren't the Sanhedrin afraid?
With John Calvin's help, I came to the understanding that Luke simply meant Stephen's face showed a certain calm and even joy in the midst of a fearful opposition; and it is in this manner, he had an angelic face. This may not be one of the more exciting interpretations out there (since it takes the fantastic lights out of the passage!), but I believe it's a sound one.
According to Calvin, another Old Testament reference would be more fitting. Namely Achish’s words to David, “From the day you came to me until now, I have found no fault in you, but the rulers don’t approve of you…I know that you have been as pleasing in my eyes as an angel of God” (1 Sam. 29:6-9). Calvin writes in his commentary, "Luke says that Stephen appeared like an angel; this is not spoken of his natural face, but rather of his present countenance. While the countenance of those arraigned are commonly pale…Luke teaches that there was no such thing in Stephen, but appeared in him a certain majesty. For the Scripture uses analogy of angels in this sense; as 1 Samuel 29:9; 2 Samuel 14:17; 2 Samuel 19:27” (Here are the two additional cross references: 2 Samuel 14:17: “…for my lord the king is like an angel of God in discerning good and evil”; 2 Samuel 19:27: “My lord the king is like an angel of God; so do whatever pleases you”).
Calvin's take is especially strong given the context that “face of an angel” is not something that would have led anyone to be afraid. Rather, such confidence in God's judgment and the peace that comes from it would strike as defiance to those who would pronounce condemnation based on a worldly standard of righteousness. I could see why such an angelic face would have been upsetting to the Sanhedrin. I just hope I could display this gospel radiance in my face as well.