How does this Jewish vow affect the doctrine of grace Paul so earnestly preached?
ESV - 23 Do therefore what we tell you. We have four men who are under a vow.
Acts 21:27 “When the seven days were almost completed, the Jews from Asia, seeing him in the temple, stirred up the whole crowd and laid hands on him.” Notice the phrase “when the seven days were almost finished…” But we KNOW he did purify himself on the first day himself because Acts 21:26 says so. He just didn't get to complete all the seven day rites in accordance with Num 6:9-12. I don't feel Luke is trying to get us to focus on Paul not being able to complete the vows. The point is, he did in fact seek to contradict the rumors by following through with the vows and with sacrifices (Acts 21:24). As we read this passage, at first it does seem as if we have two seemingly contradictory convictions or concepts occurring in the text. I say “seemingly” because in point of fact, the Bible cannot contradict itself. Allow me to articulate what I believe the unspoken “contradictions” are, and then allow me to attempt to harmonize them. As one reads through the Bible with eyes opened by faith, one comes to the following conclusion affirmed by “Conviction A”: Jesus came to bring the sacrifices to their fullness by his once and for all sacrifice on the cross and in doing so accomplished our eternal redemption (Rom 3:24; 1 Peter 2:24; Ephesians 1:7; 1 Peter 1:3-5). As a Christian, I hold with a firm conviction to “Concept A.” As one reads through the TaNaKH (OT), one must come to the conclusion implied by “Concept B” that as long as the Temple stood, atonement existed on two levels: temporal and eternal. Temporal atonement for the worshippers as well as for the Holy Sanctum was procured by offering the mortal blood of animals on the altar at the Sanctuary. This temporal atonement ONLY provided “sanctification for the purification of the flesh” (Lev. 16:16 corroborated with Heb. 9:13, 14 demonstrate this temporal atonement explicitly). Conclusions: If Paul is bringing a sacrifice AFTER Yeshua has already accomplished his finished work on the cross, YET while the Temple was still standing in Paul’s day, then the only conclusion that harmonizes “Concept A” with “Concept B” is that Paul’s animal sacrifices were for temporal atonement ONLY. He still affirmed in his heart and spirit that Yeshua’s blood afforded him eternal atonement. I don't have a problem with Paul’s sacrifices because I don't believe Paul felt his sacrifice competed with Yeshua’s sacrifice on the cross. Indeed, as the Heb 9:13, 14 passage shows us, they work in tandem as long as there was a standing, functioning Temple. Of course, temporal atonement is a moot point today since there is no Temple. Lastly, if my stated conclusion is invalid (and there are other possibilities that I did not cover in this short space), then one is left with Paul either compromising on his convictions about Yeshua—a position we KNOW cannot be tenable, or we have Paul acquiescing out of fear of those Jews who were all “zealous for the Law” (Acts 21:20, 21), a position I don't feel suits Paul who demonstrated time and time again in the book of Acts that he was not afraid of opposition. Paul would not simply “become a Jew” just to win the favor of these pro-Torah Jews—especially since they were already believers. To wit, 1 Cor. 9:20 cannot be Paul’s way of approving “situation ethics,” else this would also excuse “doing wrong in order to get a chance to do right.”