Mary,
Do we have to be told what to celebrate or what not to celebrate? There are cultures all over the world that have different kinds of cultural/family celebrations that are amoral and family oriented. After they become Christian, they still celebrate some of these family events such as Birthdays, Wedding Anniversaries and the birth of Christ.
Would you go to a wedding today, where wine was flowing liberally? Do you know that some Christians would never go to a wedding like that where such "sin" is being openly displayed. Yet, Jesus went to weddings like this in His day.
Usually, wine flows at the reception, afterwards. You have already attended the wedding and don't have to stay if you think you will sin.
Peter acted one way to the Gentiles in Galatia and one way to the Jews. Jesus never acted one way to the Church and one way to Sinners. He ate and drank with Sinners at their weddings (even drinking the wine) and I am sure He would eat and drink the wine at a Christian wedding.
By the way, I don't see anywhere in Scripture where Jesus told us not to participate in weddings. There is no mention in the OT of wedding ceremonies. Yes, Jesus mentioned weddings in the NT, but the word "wedding" does not even appear in the OT.
Back to my question: Why do we think if we wash the outside of the cup, the inside will automatically be clean?
We clean up our cup on the outside so that it is presentable to a certain faction of believers who are very good at being "cup inspectors". We know who these believers are and we know exactly what kind of cup they are expecting to see.
I'm all for clean cups, but Jesus wants the inside of the cup clean. That is more of a priority with Him than the outside. While others can only see the outside of your cup, Jesus has a special vantage point in which He can see the inside, too.
Jesus does not tell us how to do everything in life, such as what celebrations to partake in or not partake in. The Lord talks about matters of the heart and if your heart does not condemn you, then don't let others condemn you. They are only looking at the outside of your cup and have no standing or authority to say that the inside of your cup is dirty.
Do we actually have the authority and insight to judge others that celebrate the birth of Christ or weddings or birthdays or annivesaries? Can we rightly judge someone's heart that decorates a tree in their house or puts a cross on their wall? Do we dis-fellowship these believers or pull away from those who celebrate something that is not found in the Bible such as Birthdays or Anniversaries?
Jesus heart on the matter is that He wants us to walk in love with our neighbor and with Him.