In 1 Corinthians 9 we have Paul talking about being all things to all people. In Acts we see Paul taking a Jewish vow and worshiping in the temple (even participating in sacrifices?). Does this give us permission and even say we should participate in such ceremonies for the sake of the Gospel?
Extending this, does this give us permisson to and say we should in general take part in other ceremonies? Should we who hold to the RPW take part and participate in worship in NPW churches and their own ceremonies which are either based on something Jewish or are their own ceremonies or tradition which may not be biblical?
For some examples, do these Scriptures teach an EPer should sing nonEP songs in nonEP church? A RPW singing "fluff" songs in a NPW church or helping or taking part in altar calls, praise teams, or something they believe is not justified in Scripture? A Sabbatarian taking part in a church Superbowl party or picnic or some other entertaining Lord's Day recreational church something that has nothing to do with God? How about a person who believes Christmas and Easter violates the RPW participating in them to win people to Christ?