“In the first month, on the fourteenth day of the month at twilight is the LORD’s Passover. Then on the fifteenth day of the same month there is the Feast of Unleavened Bread to the LORD; for seven days you shall eat unleavened bread.” Leviticus 23:4-6 (also Exodus 12 and 13; Numbers 28; Deut. 16)
Leaven (yeast) in Scripture symbolizes sin and corruption (fermentation). God instructed His people to cleanse their homes of all yeast and yeast products once a year. In modern times, this involves a thorough spring cleaning during the month leading up to Passover with a final search for crumbs the day before Passover, the Day of Preparation.
On the Day of Preparation, the Passover lamb was slain. At sundown, as that day ended, the Feast of Unleavened Bread (hag hamatzoh) began. The lamb was eaten, accompanied by (among other things) bread baked without yeast (מַצָּה matzo or matzah). The celebration lasted for a week. The names of Passover and Unleavened Bread are used interchangeably or almost synonymously (Luke 22:1).
In AD 33, the lamb God had chosen, His beloved son Jesus, was killed on Preparation Day, which fell on a Friday that year. His body had to be hastily removed from the cross, wrapped in linen and placed in a shallow grave before sundown, which ushered in the Sabbath when no work was to be done. (Mark 15:37-47; Luke 23:53-56; John 19:31-33.)
His breathing had stopped, his heart had stopped, his brain waves had stopped. His body was tightly wrapped in gravecloths. The body of the unleavened, crucified Messiah lay in the grave from Friday night through Saturday until early Sunday, the first day of the week.* During that time it did not even begin to decay–and by the third day Jesus was alive again.
Jesus had predicted his resurrection before his death. When asked by religious leaders for “a sign,” he referred to “the sign of Jonah the prophet.” As Jonah was three days and three nights “in the belly of the great fish,” so Jesus would be three days and three nights “in the heart of the earth,” Matt. 12:39-41; Luke 11:29, 30.
Jesus also told them, “Destroy this temple [meaning his body] and in three days I will raise it up.” John 2:19-22
Guards at the tomb (requested by religious leaders, granted by Governor Pilate) knew these predictions. The religious leaders told Pilate, “Therefore command that the tomb be made secure until the third day, lest His disciples come by night and steal Him away, and say to the people, ‘He has risen from the dead.’ So the last deception will be worse than the first.” Matt 27:62-66 and 28:4-15.
During those 26 to 36 hours, what the psalmist had prophesied was fulfilled: “You will not abandon my soul to Sheol; nor will You allow Your Holy One to undergo decay” Psalm 16:10. The prophetic feast God’s people were celebrating unknowingly all around him–His son’s incorruption–was being fulfilled by Jesus of Nazareth, their long-awaited but unrecognized “Bread from heaven.”
As God’s people are to cleanse themselves symbolically from all sin once a year, so we are to purify ourselves spiritually by separating ourselves from sins and works of the flesh. The apostle Paul gave the church specific examples of how to apply this principle:
“Therefore let us keep the feast, not with old leaven, neither with the leaven of malice and wickedness; but with the unleavened bread of sincerity and truth.” (1 Cor 5:8)
“Having therefore these promises, dearly beloved, let us cleanse ourselves from all filthiness of the flesh and spirit, perfecting holiness in the fear of God.” (2 Cor 7:1)
*Note: Jewish reckoning of time is found in the Jewish Talmud and the Babylonian Jerusalem Talmud (the commentaries of the Jews), which says any part, an “onan,” of the day is considered a full day. http://www.letusreason.org/doct10.htm