Of course resurrection is necessary; exhumation was not in view. Jesus said, "Destroy this temple and I shall raise it...." Entombment which exceeds three days and three nights is not a fulfillment of the sign, nor is entombment of a duration less than three days and three nights.
[ And beware that you do not buy into the heresy of self-resurrection; Jesus here is speaking of the construction of the new, living temple, which is raised or erected upon the foundation of the Apostles and the Prophets, Jesus himself being the chief cornerstone. Jesus was raised from the dead by God the Father; to argue that Jesus raised himself from the dead is to argue that Jesus did not die. ]
You must remember that the challengers demanding the sign are legal experts, and cunning to the extreme. After all, at its essence, Talmudic Judaism is an elaborate and hypocritical scheme devised to allow a man to violate the Spirit of the Law while remaining within the Letter of the Law. Men of such mindset would not fail to notice, call attention to, and capitalize upon the slightest discrepancy in fulfillment of the sign. Had the sign not been fulfilled to perfection, the Jew would have used the fact to demolish the Christian Faith.
For two thousand years now, there has been no challenge from the Jew concerning fulfillment of the sign. This profound silence on the part of the Jew constitutes one of the strongest possible arguments that the sign was fulfilled perfectly, and that Jesus was entombed for precisely three days and three nights. All told, there is the testimony of Jesus himself, the testimony of multiple writers of the Scripture, the testimony of Rome, and the testimony of the silence of the Jew; all of these witness that Jesus was entombed for three days and three nights.
Only the Papist and the Protestant are so foolish and so stupid as to turn a blind eye toward this wealth of testimony, and to swallow the preposterous argument that a fragment of a day may be reckoned as a full day. Such an argument would be laughed out of court; and the challenge of the Jew is nothing other than a legal challenge to the authority of Jesus. This being the case, there is no doubt that those bringing the challenge have subjected the evidence to the most intense of scrutiny.
Those who hold to and observe the "In by Good Friday, Out by Easter Sunday" tradition do mock and blaspheme Christ Jesus, for Jesus himself declared that the period of the Entombment is the sole sign from Heaven of the validity of his claim that his works and teaching were authorized by God the Father.
Jesus died on Wednesday; Jesus was entombed on Wednesday, just prior to sunset; Jesus was raised from the dead on Saturday, just prior to sunset.
Note well that, whether one reckons by the Talmudic concept of a day as sunset-to-sunset, or by the Roman concept of a day as midnight-to-midnight, it cannot be disputed that Jesus was raised on the Sabbath. Accordingly, the Christian has no Scriptural basis for observance of Sunday, the first day of the week, as the "Lord's Day". And the notion that Sunday is the "Christian Sabbath" is nothing more than the rubbish of tradition.