The tombs also were opened. And many bodies of the saints who had fallen asleep were raised, and coming out of the tombs after his resurrection they went into the holy city and appeared to many (Matt. 27:52-53).
I've been stumped about how to properly understand this passage, and as there are many takes on it, it behooves me to consult the premier Reformer for his shot at this curiosity. It is another hallmark of Calvin's able treatment of Scripture that he does not rush headlong into speculation but takes the wisdom-driven cautious approach.
"But here a question arises. Why did God determine that only some should arise, since a participation in the resurrection of Christ belongs equally to all believers? I reply: As the time was not fully come when the whole body of the Church should be gathered to its Head, he exhibited in a few persons an instance of the new life which all ought to expect. For we know that Christ was received into heaven on the condition that the life of his members should still be hid, (Colossians 3:3,) until it should be manifested by his coming. But in order that the minds of believers might be more quickly raised to hope, it was advantageous that the resurrection, which was to be common to all of them, should be tasted by a few.
Another and more difficult question is, What became of those saints afterwards? For it would appear to be absurd to suppose that, after having been once admitted by Christ to the participation of a new life, they again returned to dust. But as this question cannot be easily or quickly answered, so it is not necessary to give ourselves much uneasiness about a matter which is not necessary to be known. That they continued long to converse with men is not probable; for it was only necessary that they should be seen for a short time, that in them, as in a mirror or resemblance, the power of Christ might plainly appear. As God intended, by their persons, to confirm the hope of the heavenly life among those who were then alive, there would be no absurdity in saying that, after having performed this office, they again rested in their graves. But it is more probable that the life which they received was not afterwards taken from them; for if it had been a mortal life, it would not have been a proof of a perfect resurrection. Now, though the whole world will rise again, and though Christ will raise up the wicked to judgment, as well as believers to salvation, yet as it was especially for the benefit of his Church that he rose again, so it was proper that he should bestow on none but saints the distinguished honor of rising along with him." (John Calvin, Commentary on Matthew 27:52)