And Joseph said unto his brethren, I am Joseph. The effect of this announcement can be better imagined than described. Hitherto he had been known to his brethren as Zaphnath-paaneah. Now the voice and the appearance of their long-lost brother would rush upon their minds at the first sound of the familiar name, and fill them with apprehension.
Probably Joseph's discernment of this in their countenances was the reason why he asked so abruptly after Jacob. Doth my father yet live? It is not now "the old man of whom ye spake" (Genesis 43:27) for whom Joseph inquires, but his own beloved and revered parent—"my father."
"Before it was a question of courtesy, but now of love" (Alford). And his brethren could not answer him; for they were troubled (or cast into a trepidation, hence terrified) at his presence—literally, before his face.
Not only did his present greatness overawe them, but the recollection of their former crimes against him filled them with alarm.