What the law could not do in that it was weak through the flesh, God did by sending His own Son in the likeness of sinful flesh, on account of sin: He condemned sin in the flesh. 

The law, having a shadow of the good things to come, and not the very image of the things, can never with these same sacrifices, which they offer continually year by year, make those who approach perfect. For then would they not have ceased to be offered? § By Him everyone who believes is justified from all things from which you could not be justified by the law of Moses.Inasmuch . . . as the children have partaken of flesh and blood, He Himself likewise shared in the same, that through death He might destroy him who had the power of death, that is, the devil, and release those who through fear of death were all their lifetime subject to bondage. For indeed He does not give aid to angels, but He does give aid to the seed of Abraham. Therefore, in all things He had to be made like His brethren.