And seeth two angels in white sitting, the one at the head, and the other at the feet, where the body of Jesus had lain. Seeth two angels - See on John 20:6 (note). She knew these to be angels by their white and glistening robes. Matthew and Mark mention but one angel - probably that one only that spoke, John 20:13.
One at the head, and the other at the feet - So were the cherubim placed at each end of the mercy-seat: Exodus 25:18, Exodus 25:19. Lightfoot.