Can you be in fellowship with people who offer animal sacrifices to GOd? Offering an animal sacrifice is a sin, right? Often our own traditions can become "Law" to us, and anything foreign to our traditions, especially "in the church/worship service," is anathema. To expand our horizons, please consider something Paul did which might surprise you. Consider these points, and then ask, "What does this tell us about God?"
1.) Paul had taken a vow (Acts 18:18), and according to the law, upon completion of that vow, he was required to offer animal sacrifices (Num 6:13ff). WAIT WHAT!? Can't do that, right? One of the reasons he came to Jerusalem was to "present offerings" (Acts 24:17).
2.) Paul met with James and the elders in Jerusalem (Acts 21:17-18.), who mentioned that thousands of newly-believing Jews (now Christians) were still zealous for the Law (v20). These Jews had heard rumors that Paul was telling Jews outside of Judah to stop keeping the Law (v21). James and the elders wanted to reassure these people that, not only was it not true,but that Paul himself still walked according to the Law. (v24)
3.) In order to accomplish this, Paul had to purify himself, along with four others who had taken a vow, and pay their expenses to shave their heads at the conclusion of their vows (Acts 21:24).
4.) According to the law, the expenses at the conclusion of a vow included the burnt offering of a 1-yr old male lamb, the sacrifice of a year-old ewe lamb, a ram, a basket of bread, flour cakes mixed with oil, unleavened wafers mixed with oil, a meal offering, drink offerings, and a portion of his shaved hair as a burned offering (Num 6:13ff).
5.) Paul waited seven days until the offering could be made for each one of them (Acts 21:26-27).
Paul knew that the Law was not evil nor sin. The error in offering sacrifices and doing those rituals comes if one seeks to be JUSTIFIED by them, which he was not. What does this tell us about God and Christianity? Does it allow you to more easily be united with other believers who maybe do some things different?