Mark 16:5
"And entering into the sepulchre, they saw a young man sitting on the right side, clothed in a long white garment; and they were affrighted."
Cross References (ranked by relevance)
John 20:8
Then went in also that other disciple, which came first to the sepulchre, and he saw, and believed.
Matthew 28:3
His countenance was like lightning, and his raiment white as snow:
Luke 1:12
And when Zacharias saw him, he was troubled, and fear fell upon him.
Mark 9:15
And straightway all the people, when they beheld him, were greatly amazed, and running to him saluted him.
Daniel 8:17
So he came near where I stood: and when he came, I was afraid, and fell upon my face: but he said unto me, Understand, O son of man: for at the time of the end shall be the vision.