Jamieson, Fausset and Brown on Mark 16:7

7. But go your way, tell his disciples and Peter--This Second Gospel, being drawn up--as all the earliest tradition states--under the eye of Peter, or from materials chiefly furnished by him, there is something deeply affecting in the preservation of this little clause by Mark alone.

that he goeth before you into Galilee; there shall ye see him, as he said unto you--(See on Mt 28:7).