This is an interesting question. Going to strongs and look up the meaning of the words might shed some light?
grave:
G3419
μνημεῖον
mnēmeion
mnay-mi'-on
From G3420; a remembrance, that is, cenotaph (place of interment): - grave, sepulchre, tomb.
bodies:
G4983
σῶμα
sōma
so'-mah
From G4982; the body (as a sound whole), used in a very wide application, literally or figuratively: - bodily, body, slave.
saints:
G40
ἅγιος
hagios
hag'-ee-os
From ἅγος hagos (an awful thing) compare G53, [H2282]; sacred (physically pure, morally blameless or religious, ceremonially consecrated): - (most) holy (one, thing), saint.
slept:
G2837
κοιμάω
koimaō
koy-mah'-o
From G2749; to put to sleep, that is, (passively or reflexively) to slumber; figuratively to decease: - (be a-, fall a-, fall on) sleep, be dead.
arose:
G1453
ἐγείρω
egeirō
eg-i'-ro
Probably akin to the base of G58 (through the idea of collecting one’s faculties); to waken (transitively or intransitively), that is, rouse (literally from sleep, from sitting or lying, from disease, from death; or figuratively from obscurity, inactivity, ruins, nonexistence): - awake, lift (up), raise (again, up), rear up, (a-) rise (again, up), stand, take up.
appeared:
G1718
ἐμφανίζω
emphanizō
em-fan-id'-zo
From G1717; to exhibit (in person) or disclose (by words): - appear, declare (plainly), inform, (will) manifest, shew, signify.
Verses 50 and 51 are probably besides His resurrection, the most important thing that has ever happened for mankind. The new testament was ushered in, we are no longer under law, but grace. This was a huge event witnessed by many, and the honest hearted ones witnessing this were awakened out of a deep sleep, awakened to the truth, being brought out from under the curse of the law and into His glorious life. And they appeared to many declaring this truth openly, not being afraid of the consequences.
Since this is only reported only in Mathew, seems strange if this physically happened. Not only that, but the ones who so vehemently fought against the truth would of instantly been stopped in their tracks, seeing dead people walking around the city. The fear would of been too great for them to continue persecuting the early christians.
Just a thought, but I agree, if something like this would of physically happened at the time of the death of Christ, there would be much written about it.
God bless,
Gary