He rose again the third day according to the scriptures.
Here we must remember the custom of the Hebrews, for
according to the Jewish reckoning the day began in the evening
and lasted until the evening of the next day, as the first chapter
of Genesis says: "And there was evening and there was morning,
one day," "a second day," "a third day," and so forth.
Thus the first and greatest Sabbath began on the evening of
the day when Christ was crucified, that is to say, at the time
of sunset on Friday. In addition to this the Jews had seven
full days which they celebrated, and all of which they called
sabbaths. On these days they ate only wafers and unleavened
bread, for which reason they are called the days of unleavened
bread. Christ rose before sunrise.
How can we say then that he rose on the third day, since he
lay in the grave only one day and two nights? According to
the Jewish calculation it was only a day and one half; how
shall we then persist in believing there were three days? To
this we reply that he was in the state of death for at least a part
of three days. For he died at about three o'clock on Friday and
consequently was dead for about three hours on the first day.
After that night he lay in the grave all day, which is the true
Sabbath. On the third day, which we commemorate now, he
rose from the dead and so remained in the state of death a part
of this day, just as when we say that something occurred on
Easter day, although it happens in the evening, only a portion
of the day. In this sense Paul and the Evangelists say that he
rose on the third day.
For this period and no longer Christ was to lie in the grave,
so that we might suppose that his body remained naturally uncorrupted
and that decomposition had not yet set in. He came
forth from the grave so soon that we might presume that corruption
had not yet taken place according to the course of nature ;
for a corpse can lie no longer than three days before it begins
to decompose. Therefore Christ was to rise on the third day,
before he saw corruption.