Most Christians don't celebrate the Passover, since it is seen to belong rather to a Jewish or Old Testament tradition which they believe to be no longer necessary. Among those Christians who do observe the Passover, there are some differences in how this is done. Some follow the instructions that Jesus gave to his disciples at the time of his last meal before he was crucified, and share instead of roasted lamb, bread (usually unleavened) and wine. In the Christian Passover service the unleavened bread is used to represent Jesus' body, and wine represents his blood of the New Covenant (). These are a symbolic substitute for Jesus as the true sacrificial Passover "Lamb of God" (). It should also be noted that Passover day is followed in the Scriptures by seven days of unleavened bread (). These days have a great dual significance to the observant Christian. Just as leavening causes bread to be puffed up, so sin causes Christians to be "puffed up" with the sin of "malice and wickedness," and therefore must "purge out" that "old leaven" and replace it with "the unleavened bread of sincerity and truth" (King James Version - ). Therefore, in the Christian Passover service Christ's body is represented by unleavened bread symbolizing his sinless life, for he alone had no sin (). Since these Scriptures indicate that during the seven days of unleavened bread, leavening represents sin and unleavened bread represents righteousness, when Christians remove leavening during these days they are reminded to put sin out of their lives.