Acts 21:18-26, Luke records how Paul participated in a ceremonial Jewish purification rite involving offerings under the law which I presume to involve sacrifice of some type of animal.
The question arises as to why did Paul submit to this ritual given his faith in the sufficiency of Christ sacrifice at the cross. Did Paul sin in so participating. Well, certainly Paul like Peter in Galatians 2 was capable of doing wrong as biblical apostles were not perfect as no one in human flesh other than the pre-resurrected Jesus was/is perfect.
But let us consider another explanation. The law is righteous. So it is not unrighteous to offer animal sacrifice for sins. But we know now that sacrifice was/is insufficient.
Paul of course knew it was insufficient. He had already preached it. They knew he had preached it. But I don’t know of any scripture where he said it was sinful to offer animal sacrifice.
So it seems Paul went along with doing that which is righteous to do in order to try and avoid unnecessary conflict. But even that did not work. For the people later came against him anyway (Acts 21:27-36).
Paul did a similar thing in Acts 16:1-3 regarding Timothy. Paul speaks about this approach in 1 Cor 9:19-23 and 1 Cor 10:23-33.
During biblical days people were yet offering sacrifices within at least Jewish Christian communities but this was clearly not an expectation within Gentile Christian communities (Acts 21:25; Acts 15). But at least since the temple destruction there has been no animal sacrifices within the Jewish communities and certainly not within the Jewish Christian and Gentile Christian communities.
