On The Holy Trinity by St. Augustine
Chapter 6.--The Three Days of the Resurrection, in Which Also the Ratio of Single to Double is Apparent.
10. Scripture again witnesses that the space of those three days themselves was not whole and entire, but the first day is counted as a whole from its last part, and the third day is itself also counted as a whole from its first part; but the intervening day, i.e. the second day, was absolutely a whole with its twenty-four hours, twelve of the day and twelve of the night. For He was crucified first by the voices of the Jews in the third hour, when it was the sixth day of the week. Then He hung on the cross itself at the sixth hour, and yielded up His spirit at the ninth hour. But He was buried, |now when the even was come,| as the words of the evangelist express it; which means, at the end of the day. Wheresoever then you begin, -- even if some other explanation can be given, so as not to contradict the Gospel of John, but to understand that He was suspended on the cross at the third hour, -- still you cannot make the first day an entire day. It will be reckoned then an entire day from its last part, as the third from its first part. For the night up to the dawn, when the resurrection of the Lord was made known, belongs to the third day; because God (who commanded the light to shine out of darkness, that through the grace of the New Testament and the partaking of the resurrection of Christ the words might be spoken to us |For ye were sometimes darkness, but now are ye light in the Lord| ) intimates to us in some way that the day takes its beginning from the night. For as the first days of all were reckoned from light to night, on account of the future fall of man; so these on account of the restoration of man, are reckoned from darkness to light. From the hour, then, of His death to the dawn of the resurrection are forty hours, counting in also the ninth hour itself. And with this number agrees also His life upon earth of forty days after His resurrection. And this number is most frequently used in Scripture to express the mystery of perfection in the fourfold world. For the number ten has a certain perfection, and that multiplied by four makes forty. But from the evening of the burial to the dawn of the resurrection are thirty-six hours which is six squared. And this is referred to that ratio of the single to the double wherein there is the greatest consonance of co-adaptation. For twelve added to twenty-four suits the ratio of single added to double and makes thirty-six: namely a whole night with a whole day and a whole night, and this not without the mystery which I have noticed above. For not unfitly do we liken the spirit to the day and the body to the night. For the body of the Lord in His death and resurrection was a figure of our spirit and a type of our body. In this way, then, also that ratio of the single to the double is apparent in the thirty-six hours, when twelve are added to twenty-four. As to the reasons, indeed, why these numbers are so put in the Holy Scriptures, other people may trace out other reasons, either such that those which I have given are to be preferred to them, or such as are equally probable with mine, or even more probable than they are; but there is no one surely so foolish or so absurd as to contend that they are so put in the Scriptures for no purpose at all, and that there are no mystical reasons why those numbers are there mentioned. But those reasons which I have here given, I have either gathered from the authority of the church, according to the tradition of our forefathers, or from the testimony of the divine Scriptures, or from the nature itself of numbers and of similitudes. No sober person will decide against reason, no Christian against the Scriptures, no peaceable person against the church.