Jamieson, Fausset and Brown on Daniel 12:4

4. shut up ... seal the book--John, on the contrary, is told (Re 22:10) not to seal his visions. Daniel's prophecy refers to a distant time, and is therefore obscure for the immediate future, whereas John's was to be speedily fulfilled (Re 1:1, 3; 22:6). Israel, to whom Daniel prophesied after the captivity, with premature zeal sought after signs of the predicted period: Daniel's prophecy was designed to restrain this. The Gentile Church, on the contrary, for whom John wrote, needs to be impressed with the shortness of the period, as it is, owing to its Gentile origin, apt to conform to the world, and to forget the coming of the Lord (compare Mt 25:13, 19; Mr 13:32-37; 2Pe 3:8, 12; Re 22:20).

run to and fro--not referring to the modern rapidity of locomotion, as some think, nor to Christian missionaries going about to preach the Gospel to the world at large [Barnes], which the context scarcely admits; but, whereas now but few care for this prophecy of God, "at the time of the end," that is, near its fulfilment, "many shall run to and fro," that is, scrutinize it, running through every page. Compare Ha 2:2 [Calvin]: it is thereby that "the knowledge (namely, of God's purposes as revealed in prophecy) shall be increased." This is probably being now fulfilled.