Exegesis:

anablepsasai (cf. 6.41) ‘looking up’: Lagrange suggests that here the verb means ‘look closely,’ ‘look attentively.’

thēorousin (cf. 15.47) ‘they notice,’ ‘they observe.’

anakekulistai (only here in the N.T.; cf. apokuliō in previous verse) ‘it has been rolled back.’

ēn gar megas sphodra ‘for it was exceedingly large’: this explanatory clause would seem logically to belong to v. 3, explaining the women’s discussion as to who should roll away the stone for them. As it stands, at the end of this verse, it seems to explain why the women noticed it had been rolled away. Several translations circumvent the difficulty by disregarding gar ‘because,’ ‘for,’ a procedure which is not to be recommended.

sphodra (only here in Mark) ‘very much,’ ‘extremely,’ ‘greatly.’

Translation:

The women may have looked at the tomb from some little distance, and hence, because of the size of the stone, they could see that it had been rolled away. This at least provides some basis for the interpretation of gar as ‘for,’ ‘because.’

Was rolled back is not technically a passive, in that the women saw the stone actually being rolled back. What they saw was the state of the stone in a rolled-back position. This means that in some languages one must translate either as a pluperfect passive of process, e.g. ‘had been rolled back’ or as a past state, e.g. ‘was in a rolled-back position.’

Quoted with permission from Bratcher, Robert G. and Nida, Eugene A. A Handbook on the Gospel of Mark. (UBS Handbook Series). New York: UBS, 1961. For this and other handbooks for translators see here .