Sitting on the right side - As they entered. The sepulchre was large enough to admit persons to go into it; not unlike, in that respect, our vaults.

And entering into the (b) sepulchre, they saw a young man sitting on the right side, clothed in a long white garment; and they were affrighted.
(b) Into the cave out of which the sepulchre was cut.

And entering into the sepulchre,.... For the sepulchres of the Jews were made so large, that persons might go into them: the rule for making them is this (k);
"he that sells ground to his neighbour to make a burying place, or that receives of his neighbour to make a burying place, must make the inside of the cave four cubits by six, and open in it eight graves; three here, and three there, and two over against them: and the graves must be four cubits long, and seven high, and six broad. R. Simeon says, he must take the inside of the cave six cubits by eight, and open within thirteen graves: four here, and four there, and three over against them; and one on the right hand of the door, and one on the left; and he must make, "a court", at the mouth of the cave, six by six, according to the bier, and those that bury; and he must open in the midst of it two caves, one here and another there. R. Simeon says, four at the four sides; R. Simeon ben Gamaliel says, all is according to the nature of the rock.''
Now it was in the court that the women entered, where the bier was to be put down by the bearers; and where they could look into the sepulchre, and the several caves and graves in it, and what were in them. So Maimonides says (l),
"they dig caves in the earth, and make a grave on, the side of the cave, and bury in; it.''
And there being a door into one of these caves, persons might enter in, and see where the graves were, and the bodies lay.
They saw a young man; an angel; as angels used to appear in the form of men: nor is this any contradiction to John's account, who says there were two angels, one at the head, and another at the feet, John 20:12; since Mark does not say there was no more than one; besides, John relates what Mary Magdalene saw, when alone, and Mark what all the women saw:
sitting on the right side; from whence we learn, on what side of the door of the sepulchre Christ was laid, according to the above description of one:
clothed long white garment: See Gill on Matthew 28:3; which was as white as snow:
and they were affrighted; at the sight of him; not expecting such a vision, but to have seen, the body of their Lord.
(k) Misn. Bava Bathra, c. 6. sect. 8. (l) Maimon. Hilch. Ebel, c. 4. sect. 4.

entering into the sepulchre, they saw a young man--In Matthew 28:2 he is called "the angel of the Lord"; but here he is described as he appeared to the eye, in the bloom of a life that knows no decay. In Matthew he is represented as sitting on the stone outside the sepulchre; but since even there he says, "Come, see the place where the Lord lay" (Matthew 28:6), he seems, as ALFORD says, to have gone in with them from without; only awaiting their arrival to accompany them into the hallowed spot, and instruct them about it.
sitting on the right side--having respect to the position in which His Lord had lain there. This trait is peculiar to Mark; but compare Luke 1:11.
clothed in a long white garment--On its length, see Isaiah 6:1; and on its whiteness, see on Matthew 28:3.
and they were affrighted.

And entering into the sepulchre. Mary Magdalene, seeing the stone rolled away, and supposing the body had been removed by the Jews, runs to find Peter and John (John 20:1-2). The other women proceed to the sepulcher, and enter.
Saw a young man. Matthew calls him an angel. Luke says that there were two who "stood;" i. e., appeared suddenly. Besides, they might easily have both sat and stood during the interview; might have been both outside and inside at different moments, and they might have been seen both singly and together in the sudden and shifting apparition.--Jacobus.