No, he says "Christ, our Passover, was sacrificed for us. Therefore let us keep the feast ... with the unleavened bread of sincerity and truth." He's talking about the Catholic Mass, if any feast at all (Chrysostom thinks that the leaven v. unleavened is simply a metaphor, and this interpretation has probability: see his homilies on I Cor.)
7 Purge out the old leaven, that you may be a new paste, as you are unleavened. For Christ our pasch is sacrificed.
8 Therefore, let us feast, not with the old leaven, nor with the leaven of malice and wickedness: but with the unleavened bread of sincerity and truth.
9 I wrote to you in an epistle not to keep company with fornicators.
10 I mean not with the fornicators of this world or with the covetous or the extortioners or the servers of idols: otherwise you must needs go out of this world.
11 But now I have written to you, not to keep company, if any man that is named a brother be a fornicator or covetous or a server of idols or a railer or a drunkard or an extortioner: with such a one, not so much as to eat.
12 For what have I to do to judge them that are without? Do not you judge them that are within?
13 For them that are without, God will judge. Put away the evil one from among yourselves.
v. 8 is showing the reason for v. 9-13: "I have written to you ... with such a one, not so much as to eat." In other words, they were to be excluded from communion.
Your interpretation makes no sense. Why would Paul have thrown a command to keep the Feast of Unleavened Bread into his discussion of the measures to take against the fornicator?
I would say that's a modern day interpretation. Paul actually goes much further. He says that anyone who calls himself a Christian yet continues to willfully engage in obviously sinful behavior should put out of the church:
1Co 5:13 But them that are without God judgeth. Therefore put away from among yourselves that wicked person.
Your interpretation makes no sense. Why would Paul have thrown a command to keep the Feast of Unleavened Bread into his discussion of the measures to take against the fornicator?
Because it shows the spiritual purpose of the holy day. The practice of seeking out and removing leaven from your household is a yearly physical reminder that we must seek out and remove sin from our lives. Paul extends the lesson to show that a sinful person in the midst of the congregation is like leavening in bread...it spreads to everyone else if tolerated. One bad apple can spoil the whole barrel.
Our sins are forgiven by Christ's sacrifice. That is represented by Passover.
God's Holy Days represent God's plan of salvation for mankind.
God does not want us to continue in sin after our sins are forgiven.
Rom. 6:15 What then? Shall we sin because we are not under law but under grace? Certainly not!
God's 2nd step in His plan of salvation is represented by the Feast of Unleavened Bread. Unleavened bread is flat, not puffed up. It is a humble bread that pictures sinlessness.
The Feast of Unleavened Bread represents our putting sins out of our life so that we may have a closer walk with God.
That is why Paul talked about the Feast of Unleavened Bread in relationship with taking measures against the fornicator.