In Matthew 12 40 he said that he would be three days and three nights in the heart of the earth. The passage has long perplexed Biblical students. The most probable explanation is that Christ adopted a mode of expression common among the Jews, and said that he should be in the grave three "evening-mornings," which the translators rendered three days and nights. The Jews also had a rule, of which there are several examples in other parts of the Bible, that any part of the onah, or period, counted as the whole. Thus the interval between the crucifixion and the burial on the Friday would be part of Friday, and would count as one "evening-morning"; from sunset on Friday to sunset on Saturday would count as the second; and from Saturday sunset to the resurrection on Sunday morning as the third. The disciples evidently regarded the Sunday as the third day, as is seen by the conversation on the way to Emmaus, when Cleopas said: "This is the third day since these things were done." (Luke 24:21.) Professor Wescott, a great New Testament scholar and one of the editors of the most widely used text of the Greek New Testament, held the view that crucifixion and burial occurred on Thursday; but practically every other authority disagrees with him. The celebration of Friday as the day of our Lord's death and burial dates back to extremely early times in Church history. It is true that the expression "three days and three nights" in the passage you mention sounds very emphatic to our Western ears, accustomed to the sharp distinction conveyed by the words in our time and speech. But, as Dr. Whedon comments here, "the Jews reckoned the entire twenty-four hours in an unbroken piece as a night-and-day. They counted the odd fragment of a day, in computation, as an entire night-and-day. Our Lord, therefore, was dead during three night-and-days."