(I) Or, by a sacrifice for sin.

(a)  Romans  8:3 what the law could not do in that  it  was  weak through the flesh
"And by him all that believe are justified from all things,  from which  ye  could not be justified by the law  of  Moses." (Acts 13:39)
"Therefore by the deeds of the law there shall no flesh be justified  in  his sight: for by the law [is] the knowledge  of  sin." (Romans 3:20)
"For  there  is verily a disannulling of  the  commandment  going before for the weakness and unprofitableness thereof. For the law made nothing perfect, but the bringing in of a better hope [did]; by the which we draw nigh unto God." (Hebrews 7:18,19)
"For  the law having a shadow of good things to come,  [and]  not the  very  image of the things, can never with  those  sacrifices which  they  offered  year by year continually  make  the  comers thereunto  perfect.  For then would they not have  ceased  to  be offered? because that the worshipers once purged should have  had no more conscience of sins." (Hebrews 10:1,2)
"By the which will we are sanctified through the offering of  the body of Jesus Christ once [for all]." (Hebrews 10:10)
"For  by  one offering he hath perfected for ever them  that  are sanctified." (Hebrews 10:14)