John Lightfoot on Mark 16:13

[Neither believed they them.] That in the verses immediately going before the discourse, the question is of the two disciples going to Emmaus, is without all controversy: and then how do these things consist with that relation in Luke, who saith, that "they...returned to Jerusalem and found the eleven gathered together, and them that were with them, saying, The Lord is risen indeed, and hath appeared to Simon," Luke 24:33,34. The word saying, evidently makes those to be the words of the eleven, and of those that were gathered together with them: which, when you read the versions, you would scarcely suspect...in the original Greek, since it is the accusative case, it is plainly to be referred to the eleven disciples, and those that were together with them. As if they had discourse among themselves of the appearance made to Peter, either before, or now in the very access of those two coming from Emmaus. And yet saith this our evangelist, that when those two had related the whole business, they gave credit no not to them. So that according to Luke they believed Christ was risen and had appeared to Simon, before they told their story; but according to Mark, they believed it not, no not when they had told it.

The reconciling, therefore, of the evangelists, is to be fetched thence, that those words pronounced by the eleven, The Lord is risen indeed, &c., doth not manifest their absolute confession of the resurrection of Christ, but a conjectural reason of the sudden and unexpected return of Peter.

I believe that Peter was gong with Cleophas into Galilee, and that being moved with the words of Christ told him by the women, "Say to his disciples and Peter, I go before you into Galilee." Think with yourself, how doubtful Peter was, and how he fluctuated within himself after his threefold denial; and how he gasped to see the Lord again, if he were risen, and to cast himself an humble supplicant at his feet. When, therefore, he heard these things from the women (and he had heard it indeed from Christ himself, while he was yet alive, that "when he arose he would go before them into Galilee"), and when the rest were very little moved with the report of his resurrection, nor as yet stirred from that place, he will try a journey into Galilee, and Alpheus with him. Which when it was well known to the rest, and they saw him return so soon, and so unexpectedly, "Certainly (say they) the Lord is risen, and hath appeared to Peter; otherwise, he had not so soon come back again." And yet when he and Cleophas open the whole matter, they do not yet believe even them.